In its historical aspect science may be likened to a tree which is constantly branching as the sum total of knowledge grows larger and larger and a subdivision of the field becomes necessary. Occasionally, a bud of special vigour appears and gives rise to a branch so dominating and important that it changes the contour of the whole organic body. An event of this nature seems to have happened in Indian Botany when the young Sahni graduated from Lahore in 1911 and proceeded to England to study further in the Botany School of the Cambridge University. Coming under the influence of a great master like the late Prof. A. C. Seward, he learnt rapidly, gained much insight and experience in the morphology of living as well as fossil plants and started a flourishing school of research on his return to India, which is now well known allover the world.

It is commonly believed that Prof. Sahni was a palaeobotanist, and that it was his work in this field which brought him many distinctions like the Fellowship of the Royal Society and the Presidentship of the Indian Science Congress. While this is essentially true, those like the present writer, who came in personal touch with him, would at once agree that he was a botanist of very wide interests, eager to take advantage of every opportunity in advancing our knowledge of plant life. When I was told by Dr. R. V. Sitholey, a former pupil of Prof. Sahni and my own, and Secretary to the Editorial Committee of The Palaeobotanist, that Prof. T. G. Halle would review his work on the palaeobotanical side, and that I should review that on living plants, I, therefore, readily acceded to his request and set out to prepare this brief sketch.

Sahni's first paper entitled "Foreign Pollen in the Ovules of Ginkgo and of Fossil Plants" was published in the New Phytologist of 1915, only a few years after he reached Cambridge. Here he recorded the presence of pollen grains other than those of Ginkgo in no less than eight out of about a dozen ovules of this plant obtained from Montpellier. Most of them showed the presence of two prothallial cells thus indicating their abietineous nature and one had germinated to form a tube twice as long as its own diameter.

Although an interesting observation in itself and quite indicative of the discerning power of the author, it is the latter part of the paper which specially revealed Sahni's critical insight even at that early stage of his career. He notes: “If a similar example were found in a fossil state, it would in all probability have led to a reference of the pollen grains and ovule to the same species". Further, the mere fact of germination cannot be used in support of conclusions regarding the identity of fossil pollen-grains found enclosed in ovules ".

Sahni's next paper, published in the New Phytologist of 1915, dealt with the anatomy of Nephrolepis valubilis, collected near Kuala Lumpur, Federated Malay States, by Prof. F. T. Brooks, at that time Lecturer in the Botany School of the Cambridge University. This is a very peculiar fern in which the enormously long stolons arising from the mother plant scale forest trees to a height of 16 metres. The lateral plants borne on them at intervals reach heights considerably above the mother plant which is rooted in the soil. Periodically the former are shed to the ground after which they produce their own roots. Sahni gave a detailed account of the anatomy of the stolon and the manner in which the basal protostele of the lateral plants becomes modified into a dictyostele. Unfortunately no part of the mother plant was available to him and, therefore, a fuller account could not be given.

From N ephrolepis valubilis Sahni proceeded to a study of the vascular anatomy of the tubers of N. cordifolia (New Phytologist, 1916) which are formed as terminal swellings of short branches of the underground stolons. The influence of the size factor on internal structure was very evident in this case. The strand of the branch stolon enters the base of the tuber as a solid protostele but rapidly expands in a funnel-like fashion, acquiring internal phloem, pericycle, endodermis and ground tissue. Eventually the expanded stele breaks up into a hollow network of tangentially flattened strands separated by gaps of irregular shapes and sizes. Towards the apex of the tuber the strands converge again to form a single protostele.

An important point here is the breaking up of the stele and the formation of gaps without any influence from leaf traces which in normal fern rhizomes have been held to be the dominating factors in the evolution of a dictyostele.

Soon after the publication of his papers on Nephrolepis, Sahni submitted a dissertation for the Sudbury-Hardyman Prize on the "Evolution of Branching in the Filicales" which was published in the New Phytologist of 1917. In this he showed that as a rule the branches do not hold any regular position with respect to leaves and those cases where such a relationship is found”, this association is, in its evolutionary origin, a secondary phenomenon attributable to possible biological advantages, one of which may be the protection of the young bud ".

New Caledonia shares with some other islands of the Pacific the possession of a large number of endemic species which are of great interest to the morphologist and systematist. Prof. R. H. Compton of South Africa, who visited these islands in 1914, collected a number of plants among which was also the rare and little known conifer Acmopyle pancheri. Originally named by Pancher as Podocarpus pectinata, then renamed by Brongniart and Gris (1869) as Dacrydium pancheri, this plant was finally transferred by Pilger to a new genus of doubtful affinity. The generic name Acmopyle, which he gave to it, refers to the so-called apical position of the micropyle although actually it is not quite so.