L YCOPODIA CE^E 5 3 



ISOSPOROUS VASCULAR CRYPTOGAMS. 



Class III. Lycopodiaceae. 



The Lycopodiaceae are a comparatively small group of plants com- 

 prised in only four genera, differing from one another greatly in habit, 

 but agreeing in the prevalence of a dichotomous rather than of a mono- 

 podial mode of branching in both stem and root, though this is by no 

 means universal. Growth is effected by a group of equivalent cells in 

 the growing point, never (except in Psilotum, Sw.) by a single apical 

 cell. The leaves are always of small size and entirely undivided ; in 

 Psilotum they are reduced to mere scales, and this genus is also entirely 

 rootless ; while in Phylloglossum (Kze.) the underground stem is tuberous. 

 The sporanges and spores are of one kind only ; the spore produces on 

 germination (where this has been observed) a green or colourless pro- 

 thallium, which carries on a much more independent existence than is 

 the case in the heterosporous orders, and bears, in the cases which 

 have been examined, both archegones and antherids. The position of 

 the sporanges varies. In the Lycopodieae it corresponds to that of the 

 Selaginelleae, on the upper side of the base of the leaf, or they are 

 crowded on special erect branches ; and here the sporanges are unilocu- 

 lar while in the Psiloteae they are plurilocular, and are grouped on the 

 main stem or on short lateral branches. Further details are best described 

 under the heads of the two orders into which the Lycopodiaceae may 

 be divided. In the monoecious prothallium the Lycopodiaceae approach 

 the Ophioglossaceae ; while in the structure of the sporophyte they display 

 a remarkable resemblance to the heterosporous Selaginellaceae. 



ORDER i. LYCOPODIE.E. 



In this order are included two genera of very different habit : Lyco- 

 podium (L.), with nearly 100 known species ; and Phylloglossum (Kze.), 

 with only one. The form and appearance of the oophyte vary greatly 

 even in the different species of the typical genus Lycopodium. The ger- 

 mination of the spores of L. inundatum (L.) has been described as follows 

 by de Bary : The endospore bursts in the form of a nearly spnerical 

 vesicle through the exospore, which splits into three valves ; the ger- 

 minating filament which originates in this way then divides by a septum 

 into a basal cell, which undergoes no further change, and a larger apical 

 cell, which divides into two rows of segments ; each segment further 

 divides by a tangential wall into an inner and an outer cell, so that 



