150 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



sion and commission as I will endeavour to shew 

 elsewhere.* 



In textbooks of Botany the anatomy of the genus is 

 invariably based on certain well known but incomplete 

 (in the sense that they only treat of one or more special 

 points) monographs on a few of the more commonly 

 cultivated species, such as S. Kraussiana, S. caulescens, 

 S. inaequalifoUa, &c, and no figure is more familiar to 

 students of the Vascular Cryptogams than the wood-cut of 

 the transverse section of the stem of S. inaequalifoUa, 

 originally drawn from Sachs' classic textbook. The 

 general accounts based on these researches are found to 

 be by no means applicable to all the species ; indeed 

 several peculiar conditions have, so far as I am aware, 

 never been described at all. In the research already 

 alluded to I have established eight distinct but related 

 types of stem structure as follows : — 



1° In S. Icevigata, Bak. var. Lyallii, Spr. In this 

 form a distinct rhizome gives origin to a series of 

 erect shoots on one side and roots on the other. 

 The rhizome contains a cylindrical hollow stele with 

 protoxylems on the outer border of the xylem. The 

 centre of the cylinder is occupied by a median cord 

 of metaxylem without any protoxylem elements, itself 

 however a isolated part of the outer cylinder. The 

 erect shoots on the other hand possess four cords 

 which bear the leaftraces and several accessory cords 

 which anastomose at intervals with the four primaries. 

 2° S. spinosa, P.B. In this species there is no marked 

 distinction between a rhizome and erect shoots ; the 

 stem is at first creeping and then becomes erect 

 or semi-erect. The creeping portion however shews 

 the anomaly of having a central protoxylem. Dan- 

 * The Anatomy of Selaginella. Annals of Botany, June, 1S9J-. 



