Butters: observations on rhodymenia. 211 



Reproductive i^'act. — Cystocarf (Fig. 7-12). The cystocarp 

 projects on one side of the thallus. The pericarp is composed 

 of thickened cortical tissue, which, in the mature cystocarp, is 

 8-40 cells thick. The outer walls of the pericarp are small 

 and resemble those of the cortex of the vegetative part of the 

 frond. The inner cells are large (14 x 29 mic), flattened paral- 

 lel to the surface of the cystocarp and show numerous irregu- 

 lar protoplasmic connections. The cystocarp opens by a carpo- 

 stome situated at the apex of the pericarp. 



The sporogenous tissue is in the form of an irregularly lobed 

 mass, borne on a basal placenta, and partially filling the cavity 

 of the cystocarp. The space between the spore mass and the 

 pericarp is filled with gelatine. The placenta is a mass of small- 

 celled tissue containing numerous intercellular spaces, which 

 rests upon the large-celled central tissue of the lamina. The 

 gonimoblast filaments (Fig. 9-1 1) branch repeatedly. They 

 consist of irregular elongated or rounded, often club-shaped 

 cells, with dense, finely granular protoplasm and very trans- 

 parent walls. They contain no starch. They are connected 

 in filaments by very broad protoplasmic connections surrounded 

 midway by a callous-like ring. The upper cells of the fila- 

 ments are smaller and more rounded than the lower. The 

 structure of the filaments was best shown in preparations made 

 by pressing out the contents of a mature cystocarp upon a mi- 

 croscopic slide, staining lightly with iodine in potassium 

 iodide, and then pressing out with a cover glass. The spores 

 themselves are irregular, ovoid, thin-walled cells, densely 

 packed with floridian starch. Their average size is 21.5 x 34.5 

 mic, but they vary considerably in this respect. The number 

 of spores produced in each cystocarp is very great, 20,000-30,- 

 000 being not uncommon. The lowest lobes of the sporogenous 

 mass appear to be in all cases sterile. They form small masses 

 of compact tissue consisting for the greater part of cells having 

 about one-half the diameter of mature spores and containing 

 but little starch. A few long cells like those of the goni- 

 moblast filaments also occur in this region. 



In many cystocarps branched filaments of cells rise from the 

 vegetative tissue at the base of the cystocarp. The cells of 

 these filaments (Fig. 8) exhibit peculiar lateral outgrowths 

 which appear to fuse with the adjacent cells or with similar 

 outgrowths from them, forming a peculiar loose, irregularly 



