present, however, I propose to notice only those of the Sequoia. Those on the yew may be advantageously reserved till I have to discuss the history of the Fortingall yew; which I hope to lay before the Botanical Society at its next meeting; but the observations on the Picea, Deodar, and Araucaria, &c., require another season's experience before being sufficiently matured.

The Sequoias a and b grow on the Botanic Garden terrace, in front of the main line of hothouses, one near the east, the other near the west end. They grow tolerably free; that is, their foliage is not interfered with by any neighbouring trees; and consequently their lower branches, according to the usage of young Sequoias, are thrown out far and vigorously. They are about twenty years old. A is 25 feet 4, b 26 feet 6, in height. C and d are in a clump of fifteen in the Pinetum formed in what was some years ago the Experimental Garden of the Horticultural Society. C is 19 feet 5, d 21 feet 10, in height. The lower branches of both are beginning to feel the cramping effect of a crowd; and, as a consequence, their top-shoots show more tendency to retain a vigorous upward progress than is usually observed of this species when grown as a single tree detached from all others.

On consulting the table, it will be seen that Mr M'Nab has been fully borne out in recommending for observation the Sequoia as a vigorous evergreen. The least radial width of wood made by any of them during last season of growth was a fifth of an inch; and two of them made a third of an inch. Notwithstanding their luxuriant evergreen leaves they made no wood during the winter months. But they made an early start in this respect in the spring, two of them, indeed, to all appearance even before April, when not a bud was to be seen opening on any deciduous tree; and they have all made decided progress in growth of wood during our cold month of May, while most deciduous trees have been stationary, or nearly so. The growth of the two in the clump has differed in each, though they are circumstanced quite alike in point of locality; for indeed their branches. actually meet. So also the two on the terrace present an equal difference; and nevertheless their exposure, and presumably their soil, are the same. I am not prepared to say

what the cause of these differences may be. bable that in similar cases the cause may following circumstance.

But it is But it is prodepend on the

It must have been noticed by all who are interested in the culture of the Sequoia, in this neighbourhood at least, that it has a strong tendency to throw away its annual produce of wood upon the lowest portions of its stem; so that, when a young plant of 20 feet or even less in height, it puts on the swollen pyramidal, or lighthouse-like form of the base, which most other trees present only at a venerable age. The same tendency is very remarkable in the Deodar. I presume it is owing to the low branches, even those running out along the ground, being usually allowed free scope to multiply themselves unduly and to extend themselves luxuriantly far outward.* Surely this is a mistake in culture. The Deodar and Sequoia are thus extremely pretty as shrubs; and hence probably the unwillingness to meddle with them. But the result is that they are extremely apt to become cripples as they grow up. The top shoot is ere long enfeebled by the demands of the numerous long low branches; and it bends over, or forks, and will no longer shoot upwards freely as it ought to do. Is the physiological cause that the branches supply the "pabulum" for making wood to that part only of the trunk which is below their junction with it?

Various forestry devices have been proposed, with variable success, for preventing this tendency and keeping the top-shoot in vigour. Many years ago I drew the attention of Mr M'Nab, senior, to this unhappy failing on the part of the Deodar, and urged a trial of planting a moderate clump of young trees at such proximity to one another as to destroy very gradually one another's low branches in their progress, as happens in the usual way of planting a young wood of more familiar Pinaceous trees. But in those days the garden could not afford space enough. M'Nab, junior, however, in planning the Pinetum in what was the Experimental Garden, resolved to make the trial; and by and by the result will be seen both with the Sequoia and the Deodar. I may here add that the only

Mr

* In many the branches are so thickset, that it is impossible to find an accessible spot for measuring the trunk.

specimens I have seen near Edinburgh of these two species exhibiting their native tendency to shoot vigorously upwards, have been trees which for one reason or another showed only small and few branches on many of the lower feet of their trunks.

I have said that the Sequoia and other evergreen trees do not increase their trunks during the winter season. They did not do so during the past hard and prolonged winter. But it is possible that matters may be otherwise in another winter exceptionally mild, such as we have had not long ago. At all events I expect another year's observations will confirm those of the year which is past in indicating, that in the temperate-houses, as well as in the palm-house, evergreen trees of the Pinaceous order make trunk-wood equally well in the winter and the summer months.

Let me add that on several occasions I have been startled to find that trees thought healthy were making little or no progress in enlarging their trunks. Minute examination then detected other grounds for fearing that they are going wrong. But it is well to subject these trees to another season of observations before pronouncing positively what is to be their fate.

III. Recent Researches relative to the Botanical Source of the Turkey (or Russian) Rhubarb-root of Commerce. By Sir ROBERT CHRISTISON, Bart., V.-P. R.S.E.

(Read 12th June 1879.)

In the Botanical Society's "Transactions" for 1877 a short notice appeared of the recent discovery of the true rhubarb plant near the sources of the Hoang-ho river by the Russian traveller Colonel Prejevalsky, and of its introduction into the Edinburgh Botanic Garden by means of young plants raised at St Petersburg from seeds sent by the traveller to Professor Maximinovitch, Professor of Botany at the Russian capital. The circumstance, that these plants have now come into full flower in the garden, and for the first time, it is believed, in Britain, renders it a

TRANS. BOT. SOC. VOL. XIII.

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matter of interest that the relation of Prejevalsky's species to other species of Rheum previously known, and to the past botanical and horticultural history of rhubarb, should be now stated somewhat systematically, on account of the important practical consequences which may not improbably flow from this discovery.

I must set out with observing that recent systematic writers have been apt to lose sight of the earliest, and still the most important, of the inquiries prior to those of Prejevalsky, into the botanical source of the fine qualities of commercial rhubarb-root-viz., the account of the cultivation and characters of the Rheum palmatum given in 1765 by Dr John Hope, Professor of Botany in the University of Edinburgh, in the "Philosophical Transactions," vol. lv. p. 290. Thus, in a most valuable work, the "Pharmacographia " of Flückiger and Hanbury, published in 1874, there is a very learned summary of the literature on the subject, from the travels of Marco Polo and Purchas' Pilgrim, downwards to the present day; but the name of Professor Hope is not so much as once mentioned. In the no less learned notice taken of the subject by Mérat in his "Dictionnaire de Matière Médicale" Hope's investigation is equally omitted. His share in the inquiry however was succinctly referred to by Dr Pereira in 1850 in his "Elements of the Materia Medica," ii. 1344, as it had also been previously in my "Dispensatory" in 1842.

As it seems now almost demonstrable, that Hope's plant is after all the true source of the finest rhubarbroot, and his paper in the "Philosophical Transactions" is difficult of access, and likely now to acquire fresh importance, no apology is needed for reproducing here a few passages from his pithy narrative. These are indeed peculiarly interesting, because they may be employed nearly word after word to describe the history and characters of the new plants in the Botanic Garden; and his illustrative drawing, taken obviously with great care, might equally be employed to illustrate the principal one of these plants.

Dr Hope's paper begins thus:" Edinburgh, Sept. 24, 1765. In autumn 1763 I received from Dr Mounsey the seeds of the Rheum palmatum, which he assured me were

I sowed them immediately

the seeds of the true rhubarb. in the open ground in the Botanic Garden. In the beginning of May last one of the plants from these seeds pushed up a flowering stem, and about the middle of the month the flowers began to open, and continued in great beauty till the 8th or 9th of June. During this period the wind was from the east, and extremely cold; and both the air and ground very dry. These circumstances had a great effect on the flowers; for at their first appearance one cold day many of them turned black, and I imagined they would have been totally destroyed. They recovered however, and opened very well; and I had the pleasure of collecting nearly thirty seeds, some of which, I hope, will prove fertile." It is not stated in the narrative; but from these seeds the species has been propagated in the Botanic Garden ever since; and it has always been a tradition in the Garden, and was indeed mentioned, if my memory do not play me false, by Professor Rutherford when I attended his lectures on botany in 1813, that Hope communicated the plant far and wide to the curious both in this country and on the Continent.

Hope goes on to observe-"I was so much afraid the severity of the cold would destroy the flowers that I caused the drawing of the plant to be taken when it was four feet high; but in less than fourteen days it grew to eight feet, and at that time was most beautiful, with numerous and lofty panicles of flesh-coloured flowers, and large elegant leaves at its base."

The new plants were obtained early in 1877. About the beginning of May in the present year, the precise date was not noted,—they began to push up flowering stems. During the next five weeks of most unusually cold weather and east winds, exactly such a season as Dr Hope described that of 1765 to have been, one of the plants has produced a magnificent stem covered with flowers, and measuring on 12th June 8 feet 10 inches. The other, in a more shady situation, is behind that one both in progress and in splendour of inflorescence. I leave to Dr Balfour the scientific account of its characters, and may merely mention that the only differences now appreciable between this plant, and one flowering for comparison beside it, the pro