DEVELOPMENT OF PLANTS 



191 



Rhodophyceae, particularly the sexual method, presents so many 

 modifications and specializations that only the general features 

 can be pointed out. Singularly the spores and gametes have 

 lost their motility. Asexual reproduction is extensively brought 

 about by spores that are usually formed in fours from a mother 

 cell (Fig. 126) and therefore called tetraspores. These spore- 

 forming mother cells arise singly on the surface or in the tissues 

 of the plant, or they may be associated in conspicuous groups. 

 The spores escape from the mother cell as naked bodies and 

 finally secrete cell walls and develop into new plants. The sexual 

 method of reproduction is the most complicated among all the 

 algae, and even in the simplest form is far in advance of any 

 method heretofore noted. The female gametangium resembles 

 a flask with a long neck and is usually developed at the end of 

 a branch (Fig. 127, A), see Coleochaete. The single female 

 gamete is found at the base of the flask. The male gametes are 

 produced singly in small cells also at the ends of branches and 

 they are often closely aggregated in dense clusters (Figs. 127, an] 







FIG. 127. Sexual reproduction in Nemalion: A, tip of branch bearing 

 female gametangium, c, and cluster of male gametangia, an, from some 

 of which the motionless male gametes are escaping. B, first division of 

 the germinating gametospore, g. C, later stage showing the early forma- 

 tion of the branches from which the spores will be developed. D, spores 

 forming at the ends of the numerous branches. 



