516 



BOTANY 



PART II 



numerous depressions and protuberances prolonged into filaments. At the apex of 

 the spore the perispore expands into three pear-shaped appendages. The massulae 

 become attached to the perispore. The wall of the sporocarp is ruptured at its 

 lower portion, the apical portion 

 remaining attached to the spore in 

 the form of an ampulla-like covering. 

 The formation of the prothallia is 

 effected in essentially the same way 

 as in Salvinia, except that only one 



FIG. 482. Marsilia salvatrix. A, Sporo- 

 carp ( nat. size) ; st, stalk. JJ, Sporo- 

 carp opening in water, showing the 

 emerging mucilaginous cord. C, The 

 mucilaginous cord (</) ruptured and fully 

 extended ; sr, soral chambers ; sch, hard 

 shell of the sporocarp. D, An immature 

 sorus ; 'ma, macrosporangia ; mi, micro- 

 sporangia. (After J. SACHS and J. HAN- 

 STEIN.) 



FIG. 483. Marsilia quadrifolia. Development of 

 the male prothallus from the spore. A, The 

 spore ; B, a small prothallial cell (p) is cut off 

 by the wall (1) ; C and D, further divisions, sj, 2, 

 the mother-cells of the spermatogenous tissue 

 in the two antheridia; E, mature condition, two 

 groups of 16 spermatozoids having developed from 

 sj and s 2 > ne * n the substance derived from the 

 breaking down of the peripheral sterile cells; F t 

 a spermatozoid, highly magnified, showing the 

 cilia arising from the elongated blepharoplast 

 lying beside the spirally-wound nucleus. (After 

 LESTEK W. SHARP.) 



antheridium with eight spermatozoids arises on each of the small male prothallia 

 protruding from a massula. 



The sporocarps of the Marsiliaceae ( 122 ) have a more complicated structure : those 

 of Pilularia globulifera are divided into four chambers, each with a single sorus ; in 

 Marsilia they enclose numerous sori (14-18) disposed in two rows. The sori in both 

 genera contain both micro- and macro-sporangia. These arise as in many ferns from 

 superficial marginal cells and come to lie in cavities by the upgrowth of the sur- 

 rounding tissue. The outer layers of this become differentiated to form a hard coat. 



