20 Brannon. — The Structure and Development of 



continues. Thus a cone-shaped wall is developed about the 

 cystocarp, and a carpostome, very rarely two, is formed in 

 the apex of the cystocarp by the circularly-arranged terminal 

 cells of the pericarpic filaments. 



The lower cortical tissue, composed of a few cells at the 

 time of the fertilization of the procarp, begins to increase 

 immediately after fertilization and forms a supporting tissue 

 of four to six layers of cells between the floor or basal cysto- 

 carpic cells (consisting of the five auxiliary and the surround- 

 ing cells lying in the horizontal plane of the frond) and the 

 pericarp, enclosing the lower portion of the cystocarp 

 (Fig. 33 c). These cortical cells have thin walls and clear 

 granular contents, indicating that their function is, at least 

 partially, transmission of food to the mother-cells of the 

 sporiferous filaments. 



The body-cavity enlarges, pari passu, with the development 

 of numerous sporiferous and sterile filaments, the latter 

 connecting the cortical tissue at the base of the cystocarp 

 with various portions of the rapidly developing pericarp. 



These sterile filaments consist of a few, long, narrow cells 

 having an appearance similar to that of the cortical cells 

 (Figs. 1 8, 36 sf). The function of these filaments is somewhat 

 problematical. The fact that they originate from the basal 

 cortical region of the cystocarp, which is in immediate contact 

 with the group of dense, protoplasmic, auxiliary cells, from one 

 of whose daughter-cells the sporiferous tissue develops, and 

 that they are joined to the pericarpial wall, strongly suggests 

 that their function is to conduct nutritive material from the 

 pericarp through the cortical tissue to the mother-cells of the 

 sporiferous filaments. It seems hardly probable that they 

 afford a support to the pericarp, as it is composed of two to 

 three layers of cells arranged in the manner of an arch about 

 the body-cavity of the cystocarp (Fig. 2,1 pr). 



The fact that the cells given off in whorls from the central 

 cells of the sporiferous filaments are small with clear sparsely 

 granular contents at first, in subsequent development becoming 

 greatly enlarged and crowded with dense granular substance, 



