such large masses of the northern rocks must have taken place during the Bokkeveld-Witteberg times, represented in the south by some 5000 feet of rock. This seems to me improbable, and the only way to avoid the difficulty is to regard the Matsap beds as older than the Cape system.

Assuming that this argument is good, the Griqua Town beds, which are overlaid unconformably by the Matsap beds, must be very much older than the Cape system, and though there is no direct evidence, they may quite well be of Pre-Cambrian age.

AND PEARS IN CAPE COLONY.

By J. B. POLE EVANS, B.A., B.Sc., PLANT PATHOLOGIST.

There are two distinct diseases affecting apples in the Colony. The one under discussion in this note affects the leaves, twigs, and fruits of both apple and pear.

The fruit, the most important article from the grower's point of view, is attacked at all stages of development, but especially after the petals have fallen and the fruit is no bigger than a marble.

To such an extent is the young fruit affected at this stage that it usually shrivels and drops off.

The appearance of the disease to the naked eye is the same in al cases; usually round, rough, dark, olive-green, and velvety patches appear on the leaves, twigs and fruit.

The fruit, if it continues to grow in spite of these spots, nearly always does so at the expense of cracking.

Cutting such an apple across shows that internally it is quite healthy.

The other disease, a far more serious trouble, is known locally as "Bitter Pit."

Externally this disease is only seen on fruit which is nearing maturity, and, what is more serious still to the exporter, appears on apparently sound apples, after they have been packed in cold storage.

To the naked eye this disease appears first as smooth, darkgreen, and slightly sunken depressions usually towards the upper end of the apple. Later on these depressions turn brown, then black in colour, and entirely disfigure the whole apple, and, further, when the apple is sliced open it is spotted here and there with masses of dry brown tissue.

With regard to this latter disease we shall have nothing further to say here.

FUSICLADIUM.

As far back as 1888, Professor MacOwen attributed the disease on certain leaves and fruits of the Saffraan Pear to the fungus Fusicladium dendriticum, Fckl. He also reported that he had occasionally noted the same fungus on Apples in the Colony.

As some doubt has recently arisen with regard to this disease, I was invited to visit Cape Colony during the month of March and investigate the matter.

Some of the results of this investigation are put forward in the present note, the object of which is to show that there are two specific fungi present in Cape Colony, namely Fusicladium dendriticum, Fckl, attacking Apples, and Fusicladium pirinum, Fckl., found on

Pears.

The general appearance and occurrence of the disease in the Colony has been dealt with by Mr. Lounsbury in the Cape Agricultural Journal, No. 14, of 1905, so that without travelling over old ground we shall confine ourselves to the miscroscopic investigation.

For this investigation, a large supply of material, including diseased leaves, twigs and fruits of both Apple and Pear collected from various orchards in the Colony, was forwarded from time to time by Messrs. Lounsbury and Dewar, Government Entomologists at Cape Town and Grahamstown. In addition, while in the Colony in March, material of diseased Pear was obtained at Worcester, Paarl, Stellenbosch and Cape Town, and of diseased Apple at Stellenbosch.

All the material examined was found to be producing abundant conidia from the disease spots. From the nature of these conidia and their conidiophores, it was evident at once that we were dealing with two distinct fungi. In spite of this fact, a sharp look-out was kept to see if infected Apple material ever showed signs of being infected with the fungus found on the Pear, or Pear material to be attacked with the fungus found on the Apple. No indication of this was found in any of the examinations.

By some authorities the fungus occurring on the Apple is considered to be identical with that on the Pear; by others they are regarded as two distinct species.

To constitute a specific difference between two plants, we must be able to point to some morphological character by which we can distinguish the one from the other. A reference to the figures of these two fungi will, I think, clear up any further doubt regarding them.

FUSICLADIUM DENDRITICUM, FCKL.

In Figure I., Plate, p. 268, is shown a section through a small disease spot of F. dendriticum on the Apple, of the variety known as the Late Bloomer. It will be seen that the mycelium bursts through the epidermis, and a succession of spores is constricted off in a continuous fashion.

The ripe conidia (Figure II. a.) when sown in water soon germinate (Figure II. b.). The spore always becomes septate, and gives rise to the germ tube (Figure II. b. and c.), which eventually bears secondary spores.

FUSICLADIUM PIRINUM, FCKL.

In Figure III., Plate, p. 268, is shown a section through a disease spot on the Pear, of the "Saffraan" variety. For some little time the mycelium remains covered by the epidermis, through which it sends up here and there, stout conidiophores, which have a studded

or warted appearance, and may not unfrequently be branched. From these conidiophores the somewhat spindle-shaped spores are given off.

These spores (Figure IV., a., b., and c.) unlike those in the case of the Apple-fungus, never become septate; and, further, when they germinate, the germ tube arises at right angles to the length of the spore, instead of growing straight out, as in the case of F. dendriticum.

From this examination we are led to conclude that the disease, long known amongst Apples and Pears in Cape Colony, is due to two distinct (but closely related) fungi.

That causing disease amongst Pears is due to the fungus Fusicladium pirinum, Fckl., while that attacking Apples is caused by the fungus Fusicladium dendriticum, Fckl.

These fungi are readily distinguished, the one from the other, under the microscope, and they are identically the same as those which cause the disease known in Europe, Tasmania, Canada, America, and Australia, under various names as Fusicladium, Scab, Scurf, Black Spot, and Cracking.

Fusicladium, Figures I., II., a., b., c.; III.. IV., a., b., c.

ING THE DIAMOND-PIPES OF THE KIMBERLEY
DISTRICT.

BY ROBERT HERON RASTALL, M.A., F.G.S.

Fellow of Christ's College, Cambridge.

(Contributed by Mr. A. F. Williams, General Manager, De Beers Cons. Mines, Ltd., Kimberley, S.A.)

I. INTRODUCTION.

The manner of occurrence of the diamond bearing rocks of the Kimberley district has been so often described that it is unnecessary to do more than refer very briefly to this part of the subject. As is well known, the diamonds occur in a peculiar brecciated rock, the socalled "Blue Ground," which fills a number of vertical pipes or necks, of a somewhat cylindrical form. The mode of origin of these pipes has given rise to a great deal of controversy, but it is now generally agreed that they are of volcanic origin, although the precise type of vulcanicity which gave rise to them is still undecided. literature of the diamonds themselves and of the rock which contains them is an extensive one. The whole subject is treated exhaustively in Mr. Gardner Williams's great monograph on the " Diamond Mines of South Africa," and in a section contributed by the same authority to Science in South Africa," the official handbook of the South African meeting of the British Association in 1905.

The

The object of the present paper is rather to give a short petrographical description of the rocks which surround the diamondbearing pipes, and, in particular, of the rock types which have been exposed in the deep shafts at the Kimberley and De Beers Mines. The former has now reached a depth of 2520 feet, and the latter 2040 feet. The Bultfontein, Dutoitspan and Wesselton Mines are of much less depth, not exceeding 750 feet.

The specimens on which the following descriptions are based have been selected from two collections presented by the De Beers Co. in 1905 to the Mineralogical Departments of the Universities of Oxford and Cambridge. The specimens preserved at Cambridge were placed in my hands for determination by Professor Lewis, and Mr. Hutchinson, and I have to thank Professor Miers, of Oxford, for kindly permitting me to examine certain of the Oxford Series unrepresented in the Cambridge collection. A few of the specimens were collected by Mr. A. Hutchinson, Demonstrator of Mineralogy in the University of Cambridge, during the course of a visit to Kimberley in the autumn of 1905, when facilities for examining the De Beers Mine were afforded him by the Company. In what follows, individual specimens will be referred to by means of the numbers attached to them by the De Beers Company.

Although so much has been written on the diamonds themselves and the rock in which they are contained, there are very few references in the literature to the petrographical character of the rocks