Olson: OBSERVATIONS ON GIGARTINA. 161 



increase to three or four times their width, as seen in alcoholic 

 material, and a stratification of the walls becomes evident (Fig. 

 16, PI. 14). 



REPRODUCTIVE ORGANS. 



Cystocarps. The material studied was too far advanced to 

 show antheridia or the development of the cystocarp. 



The cystocarps are found scattered very abundantly along the 

 margin and over the surfaces of the fertile fronds. As a rule 

 they are much more abundant upon one surface than the other. 



They are borne in leaf-like proliferations of the frond and 

 are usually more or less distinctly stalked, though often they are 

 nearly sessile. Fig. 4 shows one of these leaf-like outgrowths 

 bearing no less than nine cystocarps. Generally the number is 

 smaller, from two to four (Fig. 5, PI. 13). The larger leaflets, 

 with a larger number of cystocarps, are usually found along the 

 margin. 



In form the cystocarps are subglobose with a marked indenta- 

 tion at the apex which seems to indicate a distinct carpostome, 

 but in the large number of sections observed no opening could 

 be detected. The nearest approach to it was seen in the section 

 represented in Fig. 19, PI. 10, but even here there is no sign of 

 a true pore or even of a rupture, so that evidently the cystocarp 

 is closed. From the uniform closure of the cystocarp it is diffi- 

 cult to include the plant in question with Gigartina. The struc- 

 ture of the cystocarp regions of the thallus shows the same two 

 general areas described for the stipe and lamina with the modi- 

 fication of the inner region or pith described above. The spores 

 are developed within the central region, the cortex and outer part 

 of the pith forming a true pericarp. Except at the apex both 

 areas surround the central mass of spores. Here it is covered 

 only by the cortex. 



A peculiar structure observed was one in which the surface of 

 the thallus was only slightly raised to indicate its location, and 

 numerous long filaments were seen with their tips protruding 

 slightly from the surface (Fig. 18, PI. 14). The section was 

 stained with fuchsin and the clear filaments were sharply dis- 

 tinguishable from the other cells with their granular contents. 

 They measured 150 mic. in length. 



There was some little doubt as to what should be the interpreta- 

 tion of the section represented in Fig. 18, PI. 14. The pith cells 



