RED SEAWEEDS 209 



the substance of the plant body. The plants are col- 

 lected, washed and dried and so preserved for human food 

 (blanc mange) and especially as a food 

 for convalescents. The structure of Cal- 

 lymenia is similar to that of Chondrus. 



327. Among the very commonly col- 

 lected Red Algae on either coast are speci- 

 mens of Plocamium remarkable for the 

 beauty of its color and the regularity of 

 its branching. 



Laboratory Studies, (a) It is better for the student to 

 stud}^ the li\'ing plants of this phjdum at the seashore, but the 

 beginner should not fail to make a study of such specimens as 

 may be accessible. Specimens for the study of structure should 

 be preserved in alcohol or formalin, using sea-water instead of 

 fresh water. However, much may be made out by the careful 

 examination of dried specimens which may be obtained from 

 dealers. Red Seaweeds may often be obtained ''in the rough'* 

 which can be moistened and then pressed out and dried for 

 study. Such material will often yield quite good si)ecimens. 

 Good mounted microscopic specimens may sometimes be ob- 

 tained showing the structure of the plant as well as of the sexual 

 and asexual reproductive organs. 



(b) Make careful microscopical examination of Poly- 

 si})honia using alcoholic or formalin material. Such mounts 

 should be made in sea-water or a 3 per cent, salt solution to 

 avoid the swelling of the cell walls. In the course of the study 

 the following should be noted: (i) the cellular structure of the 

 plant body, (ii) the tetraspores, (iii) the antherids, (iv) the 

 oogones (difficult to find), (v) the cystocarps with their sj^orcs 

 (carposporos). The closely related Dasya may be substituted 

 for Polysii)honia. 



(c) Study the tissue of Chondrus. 



(d) Dried specimens of some or all of the following genera, 

 mounted on heavy white paper, or cardboard, should be 

 available for macroscopic examination. 



Porphvra, ]5atrachospermum, Corallina, Grinnellia, Xito- 

 phyllum, Polysiphonia, Dasya, Chondrus, Callophyllis, and 

 Plocamium. 

 u 



