242 



GENERAL MORPHOLOGY OF PLANTS 



with the egg hair. Its nucleus makes its way inside, travels 

 down to the egg and fuses with its nucleus. The fruit case, 

 cystocarp. After fertilization, the fertilized egg buds out in 

 various directions and produces a mass of closely branched 

 threads with short cells. The terminal cells are the spores (car- 

 pos pores), and together the mass is called the cystocarp. Each 

 spore is capable of developing a new nemalion plant. 



387. Batrachospermum and Lemanea are fresh-water 

 forms with a similar method of sexual reproduction. The former 

 multiplies also by non-motile spores (often called gonidia), a 

 single spore being formed in a small globose spore case. Batra- 

 chospermum is a beautiful plant, green or purplish in color, very 

 profusely branched in dense tufts around a central axis. It 

 occurs in shallow streams and pools. Lemanea is remarkable 

 for the fact that it grows only during the winter in the coldest 

 part of the year, often underneath the ice, and in very turbulent 

 water. 



388. Tetraspores in the red algae. Many of the red algae 

 have an asexual method of reproduction in the formation of tetra- 



spores. Four spores are borne 

 in a single spore case in a very 

 regular fashion. In many 

 species, and perhaps in all, 

 they are borne on special plants 

 which do not bear sexual or- 

 gans, as in Polysiphonia vio- 

 lacea, Gracittariu, Rhabdonia, 

 etc. 



389. Fertilization in the 

 higher red algae. The proc- 

 ess is more complicated than 

 in Nemalion and the lower 

 forms. The sperm cases are 

 developed in groups, a single non-motile sperm being formed 

 in each sperm case. After fertilization the fertilized egg does 

 not directly form the spores. It conjugates directly, or by the 



Fig. 206. 



A red alga (Callithamnion), showing spore- 

 case A, and the tetraspores discharged, B. 

 (After Thuret.) 



