SUBGENEKA AND SPECIES OF SELAGINELLA. 149 



and comparison of the systems advanced by these authori- 

 ties shews at once that the basis of classification is in each 

 case the external morphological features only. Taking 

 Baker's scheme as the most recent and best known, we 

 find that he divides the genus into four subgenera, viz. : 

 Selaginella proper, Stachygynandrum, Homostachys and 

 Heterostachys, characterised as follows : — 



1° Selaginella. Ordinary leaves all alike, multifarious. 



Bracts uniform. 



2° Stachygynandrum. Ordinary leaves of two kinds 



and spreading in two planes, those of the upper 



plane smaller and more ascending. Bracts uniform. 



3° Homostachys. Ordinary leaves of two kinds, and 



spreading in two planes. Bracts also dimorphous, 



the smaller bracts in the same plane as the smaller, 



more ascending leaves. 



4° Heterostachys. Ordinary leaves of two kinds, and 



spreading in two planes. Bracts also of two kinds, 



but the spikes resupinate {i.e., the smaller bracts 



in the same plane as the larger leaves, and vice 



versa) . 



The subgenus Selaginella proper is sub-divided into 



two series according as to whether the spikes are or are 



not sharply square ; whilst the other three subgenera are 



subdivided into a large number of groups dependent 



chiefly on habit, size, and the presence or absence of 



"articulations" or swellings at the points of origin of 



branches. 



Very few species of Selaginella have been anatomically 

 examined. The largest number yet investigated is 28 

 (out of over 300 known) by Dangeard.* He can scarcely 

 be said however, to have exhausted even these ; indeed 

 he has fallen into many and serious errors both of omis- 



* Essai sur I'anatomie des Cryptogames Vasculaircs, Le Botaniste. Vol. I. 



