By H. H. W. PEARSON, M.A., F.L.S.

(Abstract.)

Field observations have been carried on in 1905 and 1906 on Encephalartos Friderici-Guilielmi, Lehm., E. Altensteinii, Lehm., E. villosus, Lém., and on the "open-veld" form of Stangeria, which is possibly merely a variety of S. paradoxa, Moore. The full paper (see Trans. S.A. Phil. Soc., Vol xvi., pp. 341-354) contains a discussion of the results obtained, the more important of which are here summarized.

In Encephalartos Friderici-Guilielmi and in Stangeria subterranean branching plays a part in vegetative reproduction which is not less important than in many ferns with subterranean rhizomes.

The cones are lateral in E. Friderici-Guilielmi and in E. Altensteinii, and the growth of the stem is in both cases monopodial.

E. Friderici-Guilielmi, which is subject to strong insolation, cones much more freely than either E. Altensteinii or E. villosusboth, especially the latter, shade-species.

In E. Altensteinii cones are not infrequent on plants growing in more or less open positions exposed to sunlight. As far as is known, they occur very rarely, if at all, on plants in densely-shaded situations. A few observations support a similar conclusion for E. villosus.

It may be that other exceptional circumstances, such as are implied in cultivation, also act as a stimulus to the production of

cones.

In E. Altensteinii branched specimens seem to occur only in illuminated situations, and usually, if not always, near waterconditions which are both favourable to nutrition.

There is a distinct probability that entomophily occurs in E. villosus. The position of the cones in Stangeria, with respect to the surrounding vegetation, points to the inefficiency of the wind as a pollinating agent.

BY A. W. ROGERS, M.A., F.G.S.

During the geological survey of the Hay district in 1905 a comparatively small thickness of rock near the top of the Griqua Town series was found to contain numerous boulders and pebbles shaped and scratched in the manner characteristic of stones that have received their final touches from the grinding action of moving ice. Their discovery gives evidence of the third known, but earliest, period of cold climate in South Africa, the other two being those represented by the glacial deposits in the Table Mountain and the Dwyka series.

These ancient glacial periods are extremely interesting from several points of view. First, they show that very far back in the earth's history the climate in the areas concerned was such that great accumulations of snow and ice were possible, and that consequently the world's climate of to-day may not be, on the average, hotter or colder than it was then. When the evidence concerns a period possibly older than the oldest known fossiliferous rocks of any country, its bearing on the physical conditions which have prevailed during the evolution of all the known forms of life becomes important. Then, again, the required explanation of the cold climates opens up great questions, which have yet received no probable solution. The fact that a rigorous climate would probably not be local in its occurrence, that it would not be confined merely to one district in this country, gives us a new means of correlating beds in distant areas.

At most places where the Griqua Town glacial rocks crop out they are very hard and dark brown or red in colour, owing to the large amount of iron oxides in them. There are several localities where the matrix is dark blue, in colour not unlike that of the Dwyka boulder beds in the south of the colony, but there is much cherty silica in it, which makes it break with a conchoidal fracture.

The dark blue rock has been found between Kort Kloof and Punt in Hay, on Good Hope in Barkly West, and at Dimoten and Monjana Mabedi, near Khosis, in the Kuruman district. The blue matrix is crowded with grains of quartz, and it also contains many small fragments of dark chert. The included pebbles and boulders are angular, subangular, or rounded, and they range up to two feet in length. Many of them are covered on one or more sides with striæ, in the manner characteristic of glacial boulders. Some of the stones are of the "facetted" type, that is, they have one or more nearly flat faces; in cases where there are two or more faces they may meet along a fairly well defined edge. These faces are well striated.

There are other facetted fragments, which were found to be especially abundant at Sunnyside in Hay, though they occur at many other places, but their faces are not striated, or they have very few and short scratches on them. These fragments are invariably pieces of chert, and their form is probably the result of fracture along joints before they were enclosed in the matrix.

Throughout a large part of the rock the pebbles and boulders are distributed without any discernible arrangement, but layers of conglomerate, two or three feet thick, made up almost entirely of well

rounded pebbles, occur immediately below the unbedded rock at several localities, and thin, lenticular layers of gravelly rock were noticed in the unbedded boulder rock at Punt and Good Hope. Below the glacial horizon there is generally found a coarse ironstained grit, several feet thick.

The boulders and pebbles are chiefly made of dark chert. Some of them are nodular lumps, usually discoidal or elliptical in shape, with a distinct banding parallel to the plane in which the two longer axes of the nodule lie. These nodules are often covered on their flatter sides with the glacial scratches. Quartzite and grit pebbles are not infrequently seen, and fragments of a white-banded marble, very fine grained, occur in the blue rock at Punt, Good Hope, and Monjana Mabedi. In the red and brown outcrops these limestone fragments are represented by cavities in the matrix partly filled with iron oxides; in the red rock the iron oxide is in the form of specular iron lining the cavity and filling it to a greater or less extent.

So far as my observations have gone, fragments of granite and other igneous rocks are not present in these beds, a striking point of difference from the other glacial boulder beds in the Colony.

The red and brown rocks certainly owe their colours to changes which have taken place subsequently to their deposition. In some of these rocks there has been an addition of iron compounds, but it is not yet known whether this access of iron is in all cases a surface phenomenon, i.e., that the iron has collected near the surface from the immediately underlying rock, or whether it has been brought from a distance. The fact that the more ferruginous and heavier varieties are particularly noticeable where the lower beds are hæmatitic jaspers, as along the west side of the Ongeluk-Witwater syncline, and the fact that the blue matrix has only been found where the lower beds are blue or brown, although there is no such change in the surface conditions as would account for the difference, make it probable that generally the increase in iron has not taken place at the present surface. In this connection it should be remarked that the processes by which the bulk of the Griqua Town beds became converted into ferruginous jaspers were completed at the time of the formation of the Dwvka boulder beds, for large pieces of rock, which very probably came from the Griqua Town beds, have been found in the Dwyka, and in Prieska and Hay the normal Dwyka still rests upon the ferruginous jaspers.

At two places, in a sluit on the west side of the Paling ridge, and near a dried-up fountain at Monjana Mabedi, the boulder beds have been found to be more thoroughly weathered than elsewhere, and they then have a most remarkable general resemblance to both the weathered glacial beds in the Table Mountain series in Pakhuis Pass, Clanwilliam, and to the Dwyka in its weathered state. The only obvious difference in the exposures is due to the absence of other than chert, quartzite and grit boulders in the Griqua Town boulder beds.

The glacial horizon has now been found to extend from near the Orange River in Hay to about 20 miles south of Kuruman, a distance

of some 115 miles from south to north. The width of the area is about 30 miles. It has not yet been found west of the Langeberg or east of the Kaap Plateau. In all cases it is succeeded by the Ongeluk. volcanic series within about 30 feet. In the Good Hope outlier there are less than 12 feet of thin, bedded, dark quartzitic rock between the two, and the same is the case at Monjana Mabedi and Punt. At Juanana the intervening beds may be 30 feet thick. Generally there is a tract of low ground between the nearest outcrops of the Griqua Town and Ongeluk series, and it is only where hills made of the latter series rise sharply from the underlying beds that the succession has been clearly seen. The glacial beds have been found to underlie the Ongeluk series over a very wide area, and in nearly every outlier of the latter, the only exception being the Paarde Vley syncline, which has not been re-examined since the existence of the glacial beds was discovered, and there can be little doubt that the succession is a conformable one.

The source whence the chert and other rocks forming boulders in the glacial beds came is still unknown. The frequence of chert nodules should prove to be of material help in settling the question, but at present such nodules have not been described from South African rocks. The only similar nodule known to me from any other rock was shown me by Mr. D. J. Haarhoff, M.L.A., in Kimberley in April, 1906, and he says it came from the blue-ground" of the Kimberley Mine. This nodule is so like those mentioned above that I am inclined to believe that they all came from the same formation. The mode of occurrence of the chert in the Campbell Rand beds is not like that indicated by the form of the chert nodules in the glacial beds.

As to the age of the Griqua Town beds, there is nothing new to say. All recent writers on the subject are agreed that these beds are older than the Cape System of the south, but there is a difference of opinion as to the probable lapse of time between them. If, with Passarge (1) and Hatch and Corstorphine (2), we regard the unconformably overlying Matsap beds as the equivalents of the Table Mountain series of Lower Devonian or Silurian age, the Griqua Town beds may not be very much older than those periods. We know that after the deposition of the Griqua Town beds there took place a great outpouring of volcanic rocks in Cape Colony, and that both the volcanic rocks and the underlying sedimentaries were subjected to earth movements and prolonged denudation before the Matsap beds were laid down. This correlation of the latter with the Table Mountain series is, however, of doubtful value. It is based chiefly on two facts; first, a certain degree of lithological resemblance, and, second, the fact that both are older than the Dwyka series, and rest unconformably upon still older rocks.

As to the lithological resemblance, when we have stated that both groups are largely made of quartzites, with occasional thin bands of pebbles and isolated pebbles, we come to the end of the similarity. (2) The Geology of South Africa, 1905.

(1) Die Kalahari, 1904.

In colour, in modes of weathering, and in general appearance, the two groups are not alike; the Matsap beds are, on the average, coarser in grain than the Table Mountain beds, and the purplemottled tints of the great bulk of the former are foreign to the latter; the Matsap beds do not give rise to the peculiarly-curved, wind-worn masses of rock, with accumulations of iron oxides and silica in some parts and a loose, sandy texture in others which have been observed in the Table Mountain sandstone, from the Pondoland outcrops to the westernmost exposures in Calvinia. The surface of the Matsap areas is covered with large and small blocks of quartzite, with rounded corners; the rock breaks down into its component grains much less readily than the Table Mountain sandstone does; in the Langebergen of Griqualand West the ground on the top of the mountains is hard, sandy soil between the outcrops and boulders of quartzite, while in the Langebergen of the south coast and other mountains made of the Table Mountain series, the interstices between outcrops are filled with loose white or black sandy soil.

The chief objection to the correlation is to be found in a comparison of the structural features of the north and south of the Colony. In the south the earth-movements which produced the ranges made of the Table Mountain series took place long after the deposition of the Dwyka series, and there is a sequence of conformable rocks from the base of the Table Mountain series into the Karroo formation. In the north there is a great gap between the Matsap beds and the Dwyka. Near Piljaar's Poort there is an outlier of the normal northern type of Dwyka till lying between the forked ends of one of the Langeberg group of hills, and one of the chief constituents of the boulders is the Matsap quartzite; there is no doubt that the northern Langebergen were in very much the same condition during Dwyka times as they are in to-day. They have probably lost something in altitude by denudation, and new valleys have been cut in them, but they stood in the same relation to the older rocks east and west of them as they do now, and they do not appear to have suffered any further crumpling. Except that these earth-movements which affected the Matsap beds in the north took place in Pre-Dwyka times, we have no direct evidence of their date as compared with the southern rock-systems, but a further comparison of the geology of the two regions will throw more light on the question. The Matsap beds are certainly some thousands of feet thick; four thousand feet can easily be accounted for in the Langebergen, near Pad Kloof, and the top is not known. These beds originally stretched over a considerable part of Hay and southern Bechuanaland, at least as far as the Paling-Gamagara and Matsap ridges, which are outliers of the formation; a great part of this sheet of rock must have been removed in Pre-Dwyka times, for at Piljaar's Poort the outlier of Dwyka till mentioned above very probably rests upon the Griqua Town beds which crop out in the immediate neighbourhood, between the Dwyka and one of the Langeberg ridges. Now, if the Matsap beds are taken to be the equivalents of the Table Mountain series, the earth movements that crumpled the northern strata and the denudation which removed