688 



BOTANY AND PHARMACOGNOSY. 



Description. Consisting of a number of dichotomously 

 branching, somewhat enlarged segments, becoming emarginate or 

 two-lobed, which arise from a slender, somewhat flattened base 

 about one-half the length of the entire thallus ; yellowish-white, 

 translucent, sometimes with fruit-bodies or sporangia embedded 



Fig. 278. Transverse section of stipe of Aspidium marginale showing epidermis 

 (E), hypodermis (H). endodermis (N) of fibrovascular bundle (V), sieve (S), trachese (T). 



near the apex of the segments ; somewhat cartilaginous ; having a 

 slight saline odor and a mucilaginous, somewhat saline taste. 



One part of Chondrus boiled for ten minutes with 30 parts of 

 water yields a solution which gelatinizes on cooling, and is not 

 colored blue by iodine test-solution (absence of starch) ; nor pre- 

 cipitated by alcohol (distinction from true plant gums) ; nor pre- 

 cipitated by tannin (distinction from gelatin) ; nor precipitated 

 by lead acetate (distinguishing it from pectin). 



