TRANSACTIONS OF SECTION K. 853 



His researches have given us a fairly complete knowledge of the organisation of 

 these arborescent Horse-tails. 



(2) The Sphenophylle(P, a remarkahle group of vascular Cryptogams, unrepre- 

 sented among living plants, but having certain characters in common both with 

 Lycopodiacece and Equisetacem, are now very thoroughly known, owing, in a great 

 ■degree, to Williamson's investigations. The discovery of the structure of the 

 fructification, absolutely unique among Cryptogams, was in the first instance 

 •entirely his own. 



(3) The Lyginodendrea. — The existence of this family, which consists of plants 

 with the foliage of ferns, but with stems and roots which recall those of Cycads, 

 was revealed by Williamson. This appears to be the most striking case of an 

 intermediate group yet found among fossil plants. 



(4) The Lycopocliacea'. — Williamson added enormously to our knowledge of 

 this great family, and proved conclusively that Sigillaria and Lepidodendron are 

 •essentially similar in structure, both genera, as well as their allies, being true 

 Lycopodiaceous Cryptogams, but with secondary growth in almost all cases. He 

 •demonstrated the relation between the vegetative organs and the fructification in 

 many of these plants, and by his researches on Stigmaria, made known the 

 structure of their subterranean parts. The different types of Lepidodendron, of 

 which he investigated the structure, were so numerous as to place our knowledge 

 of these plants on a broad and secure foundation. The paper was illustrated by 

 lantern-slides, partly from Williamson's figures, and partly original. 



4. The Localisation, the Transport, and Role of Hydrocyanic Acid in 

 Pangium edule, Reinw. By Dr. T. M. Treub, Buitenzorg, Java. 



Five years ago Dr. Greshoff made the remarkable discovery that the poisonous 

 substance contained in great quantities in all the parts of Pangium edule, was 

 nothing else than hydrocyanic acid. This interesting chemical discovery was the 

 starting-point of Dr. Treub's physiological investigations. In microchemical re- 

 searches hydrocyanic acid presents a great advantage, as compared with the gi'eat 

 majority of substances to be detected in tissues by reagents ; namely, that the 

 Prussian blue reaction, easily applicable in microchemical research, gives completely 

 trustworthy results. The appearance of Prussian blue in a cell may be accepted as 

 ■certain proof of the previous occurrence in the cell of hydrocyanic acid, no other 

 substance producing the same reaction. The leaves prove to be the chief factories 

 •of hydrocyanic acid in Pangium, though there are other much smaller local factories 

 of this substance in the tissues of other organs. The hydrocyanic acid formed in 

 the leaves is conducted through the leaf-stalks to the stem, and distributed to the 

 spots where plastic material is wanted. The acid travels in the phloem of the 

 tibro-vascular bundles. Dr. Treub regards the hydrocyanic acid in Pangium edule 

 as one of the first plastic materials for building up proteids ; he thinks it is, in this 

 plant, the first detectable, and perhaps the first formed product of the assimilation 

 •of inorganic nitrogen. In accordance with this hypothesis, the formation of hydro- 

 cyanic acid in Pangium depends, on the one hand, on the presence of carbo-hydrates 

 or analogous products of the carbon-assimilation, and, on the other hand, on the 

 presence of nitrates. These two points were proved, or at least rendered probable, 

 by a great number of experiments made by Dr. Treub in the Buitenzorg Gardens. 

 (The details of this investigation will be found in a paper published in the ' Annales 

 •de jardin botanique de Buitenzorg '). 



6. Exhibition of Models illustrating KaryoMnesis. 

 By Professor J . Bretland Farmer. 



Professor Farmer described a set of wax models illustrating the typical forms 

 passed through, and the chief variations exhibited by, the chromosomes d^riug the 



