371 



irregularly branched, some of the branches being very regularly 

 pinnate or bipinnate, others bearing a few scattered pinnules or 

 being quite barren. 



Regarding the anatomical structure we find in the apex of 

 the plant an apical cell usually rather broad with convex sides, 

 sometimes also more conical (Fig. 362 d, e). At the base of this, 

 watch-glass-shaped segments are cut off. From these segments 



Fig. 362. Gelidiopsis rigida (Vahl) Weber-van Bosse. 



a, summit of young thallus covered with hairs (about 50:1); b, longitudinal 

 section of medullary cells (about 200:1); c, d, apices of two filaments show- 

 ing the apical cell (about 500:1); e, transverse section of the thallus 



(about 70:1). 



short filaments originate, diverging in all directions and these 

 filaments are again gradually, by various divisions, transformed 

 into a medullary tissue composed of thick-walled cells all of nearly 

 the same size and an epidermal layer of densely placed small cells 

 (Fig. 362 e). From a longitudinal section it appears that the cells 

 of the medullary tissue are subcylindrical, about six times as long 

 as broad with more or less oblique walls (Fig. 362 b). 



When referring this plant to the genus Gelidiopsis M me WEBER 

 was of the opinion that it had no apical cell, OKAMURA (1. c., fig. 6) 

 being the first who observed it. Later on in the paper on "The 

 Rhodophycese of the Percy Sladen Trust Expedition" (Transact. 

 Linn. Soc., London 1914, vol. XVI, Zoology, p. 280) M me WEBER 

 has corrected this mistake. In the above mentioned paper of OKA- 

 MURA good figures of this plant are found. 



24* 



