THE CLUB-MOriSES 



547 



Fig. 376. — Martiii'a Seluginella {SelaQinella Mariensii, Sclaginella PVniily, 

 Sclagindlacew). Gerniiiiation of macrospore (»,"), cut vertically, 

 showing the female gametophyte protruding from the ruptured .spore- 

 wall (fipm) and exposing an unfertilized archegonium (ar), hut still 

 enclosing two embryos {em}A, emb-) which have been pushed down into 

 the nutritive prothallus {pr) by their suspensors {ct, et). (Pfeffer.) — 

 Native home, Mexico; much cultivated. 



Fig. 377. — Martin's Selaginella. Embryo (^}"), cut vertically to show its 

 suspensor (et), root (w), leaves (hi, hi), ligules dig, Itg), and tip of stem 

 (St). (Pfeffer.) 



projection dig) termed a ligide,^ arises, which, by secreting mucilage, 

 serves to keep the tender terminal organs from drying. 



The formation of macrospores that begin to germinate while 

 still within the sporangium, marks a most important advance in the 

 care of offspring; for by this means not onlj^ are the chances of cross- 

 fertilisation increased, but the embryo is afforded more protection, 

 and the young plantlet can be provided with a larger quantity of 

 promptly available food while preparing for independent life. Just 

 one step further is needed as we shall sec, to attain the high develop- 

 ment of parental care achieved by seed-plants. A similar differen- 

 tiation of the sijores and sporangia into male and female is found 

 also in certain types of Filicince, and in extinct Equisetina-. 



As with scouring-rushe,s and ferns, ,so with the club-moss 

 class, the modern species but feebly represent their kin of 

 the coal age. These include giant lycopods such as Lepido- 

 dendron (Fig. 278, page 301) and Sigillaria (Fig. 277, page 299) 

 wnth much-branched trunks ten meters or more in height and 

 often a meter in thickness, bearing cones as large as those- 

 of a pine tree, and forming extensive forests. 



■ Lig'ule < L. lignla, a little tongue. 



