122 



BOTANY 



cell-membranes of the sheathiug cells decay, leaving the hardened 

 inner walls projecting from the surface of the spore like the threads 

 of a screw (Fig. 93, A). 



The ripe spore-fruit falls to the bottom of the water, and after 

 a few weeks is capable of germination. The spore-contents first 

 divide by a transverse wall into a large basal and a smaller apical 

 cell. The latter contains but little granular contents, and soon 



divides again by a vertical 

 wall into two cells, one of 

 which elongates, bends 

 down, and forms a root, 

 fastening the young plant 

 to the mud. The other cell 

 (Fig. 93, A, st.) develops 

 chlorophyll, elongates up- 

 ward, and by repeated divi- 

 sions gives rise to a short, 

 simple filament the " Pro- 

 embryo," or " Protonema." 

 This develops two nodes, 

 from the basal one (Fig. 93, 

 D) of which roots are devel- 

 oped, while from the upper 

 one is formed a whorl of 

 branches, one of which soon 

 assumes the character of 

 the perfect shoot, the origi- 

 nal apex of the pro-embryo 

 not developing any further 

 (Fig. 93, B, C, *). 



FIG. 93. A, germinating spore of Chara sp.; 

 st, apex of pro-embryo; r, primary root 

 (x40). B, an older stage; sp, spore; rn, 

 root-node of pro-embryo ; k, lateral bud 

 which is to form the permanent axis (X6). 

 C, apex of pro-embryo, showing the lateral 

 bud, k (X85). D, root-node of the same 

 pro-embryo. 



Classification of Characeae 

 (Engler and Prantl, 9) 



Two families of the Char- 

 acese are recognized, but 

 they are very closely related. 

 In the Nitellese, represented by the genera Nitella and Tolypella 

 (Fig. 94), the stem is always without cortex, and the oogonium has 

 ten crown-cells. In the Charese, whose most important genus is 

 Chara, there are but five crown-cells, and a cortex is generally 

 present. 



In one species of Chara, C. crinita, the oospores are developed with- 

 out fertilization one of the few well-authenticated cases of par- 

 thenogenesis. 



