320 



SELAGINELLA 



to a terrestrial existence. Associated with the last-named feature 

 we see the differentiation of proper conducting tissue and of 

 true roots. Tliere is, moreover, a marked tendencj'' towards 



Fig. iS^. — Sehi^iiwlhi, pruthallia and embryulogy. a. front view, and 

 b. vertical section of mature megaspore witlr female jirothallus ; c, older 

 embryo ; d, spermatozoid ; e, archegonium in longitudinal section ; 

 /, microspore with contained male prothallus ; i;. voung plant still 

 attached to the megas])ore (sp.). ar.. archegonui ; c, embryo (in b) ; 

 /., large-celled nutritive tissue (in h) ; //., foot (in c) ; /.. leaves of 

 embryo ; o., egg (in c) ; p. prothallus ; r., radicle ; .V., suspensor ; Sp., 

 coat of megaspore. (a, c, and ^i,' after l-iruchman ; d after BelajeH ; 

 remainder after Pfciter.) 



division of lalsour, on the one hand lictwccn \-cgctative and 

 reproductive leaves, on the other lietween the prothalli. In 

 the h'crns all the latter are alike and Ijear hoth kiiids of sexual 

 organs, although there are occasional exceptions when the con- 



