524 



BOTANY 



PAET II 



structure of the spermatozoids, which are biciliate. The Isoetaceae, on the other 

 hand, have multiciliate spermatozoids and the emhryo has no suspensor. On these 

 grounds the two sub-classes of Lycopodinae biciliatae and Lycopodinae pluri- 

 ciliatae may be distinguished. Herbaceous Lycopods which are the forerunners 

 of Lycopodium and Selaginella are known in the Carboniferous, while Isoetes is 

 only known with certainty from the Lower Cretaceous. 



Order 1. Lycopodiaceae ( 125 ) 



The numerous widely-distributed species of the genus Lycopodium (Club 

 Moss) are for the most part terrestrial plants ; in the tropics many pendulous 



Q 



FIG. 491. Lycopodium davatum. A, Old prothallus. B, Prothallus with young plant attached. 

 C, Antheridium in vertical section. D, Spermatozoids. E, Young archegonium, the neck 

 still closed. F, Open archegonium ready for fertilisation. G, Plant bearing cones ( nat. size). 

 H, Sporophyll with an opened sporangium. J, K, Spores from two points of view. L, A young 

 subterranean sporeling still without chlorophyll ( x 10) ; /, foot ; w, root ; 6, scale-leaves. 

 (A-F and. L after BRUCHMANN.) 



epiphytic forms also occur. In Lycopodium clavatum, one of the commonest 

 species, the stem, which is thickly covered with small, awl-shaped leaves, 

 creeps along the ground ; it branches dichotomously," and gives rise to ascending 



