20 Brannon . — - The Structure and Devetopment 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. 22 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, /arz 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, 2 6 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. 21 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, 
