RHIZOCARPE^E 



33 



these bodies are therefore developed entirely within the microspore, 

 while the microspores themselves are set free completely from the 

 sporange. As in the Salviniaceae, the whole of the contents of the 

 mother-cell is not used up in the formation of the antherozoid ; a por- 

 tion remains behind in the form of a roundish turbid lump consisting of 

 protoplasm and starch -grains, which gradually becomes clearer, and 

 attaches itself, in the form of a vesicle, to the antherozoid, which in 

 Pilularia becomes soon detached, but in Marsilea remains attached to 

 the antherozoid during the greater portion of the period of ' swarming.' 

 When the antherozoids are mature the exospore of the microspore 

 bursts at its apex, and the endospore swells up into a hyaline bladder, 





FIG. 16. Pilularia globulifera L. Longitudinal 

 section of megaspore. a, coat of spore ; b, c, 

 d, the three layers of the epispore. (After Luers- 

 sen, magnified.) 



FIG. 17. Marsilea salvatrix. Micro- 

 spore discharging antherozoids. ex, 

 exospore ; dl, endospore ; zz, anthe- 

 rozoids ;yy, their vesicles with starch- 

 grains. (After Goebel, X3so.) 



which finally bursts to allow of the escape of the antherozoids with their 

 vesicles. In Pilularia the antherozoid consists of only four or five coils 

 with a few vibratile cilia ; in Marsilea it is of considerable length, the 

 shape of a corkscrew, and consists of twelve or thirteen coils, the vibra- 

 tile cilia being also of great length. The antherozoids collect, in large 

 numbers, in the funnel-shaped depression of the epispore of the mega- 

 spore above the prothallium (see fig. 15), and force themselves, through 

 the neck of the archegone, to its central cell. 



In its early stages the development of the oosperm or impregnated 

 oosphere corresponds to that of Salviniacese. After becoming invested 

 with a cell-wall of cellulose, the first segmentations give rise to the 



D 



