326 



THALLOPHYTES 



much desired by some people. The form called Irish Moss, 

 shown in Figure 281, is collected in large quantities and employed 

 in the manufacture of jelly, which is used directly as food and as 

 the basis for the preparation of other foods. Agar-agar, which 

 is used as a medium in which Bacteria and Fungi are grown, is a 

 gelatinous product obtained from Red Algae. 



Nemalion. — This plant is one of the simpler forms of Red 

 Algae. The plant body is a rather soft, cord-like, branching 



Fig. 282. — Reproduction in Nemalion. A, a portion of Nemalion, bearing 

 antheridia at a and at the right a procarp consisting of carpogonium (c) and 

 trichogyne (() to the tip of which two sperms have become attached; B, 

 fertilized carpogonium beginning to develop branches on the ends of which 

 the carpospores are borne; C, mature cystocarp consisting exteriorly of carpo- 

 spores. X 100-150. Redrawn with modifications from Bornet. 



structure, composed of a large number of filaments, which are 

 held together by a stiff gelatinous substance. There is a central 

 axis of delicate threads and an outer region consisting of short 

 branches pointing outward. 



Nemalion produces both spores and gametes {Fig. 282) . The 

 two kinds of reproduction are intimately related, for the produc- 

 tion of spores follows closely as a result of fertilization. 



The female sex organ, which is a very peculiar structure in the 

 Red Algae, is called a procarp. In Nemalion the procarp is borne 



