OF ARTS AND SCIENCKS. 55 



by a vertical one, which thus divides the spore into four parts, pro- 

 ducing a very typical cruciate tetraspore (Fig. 12). Sometime-; in tlie 

 two-celled stage the longitudinal division of the distal cell precedes that 

 of the proximal one, giving the spore the appearance of being tripar- 

 tite. The longitudinal wall of the proximal cell is ultimately formed, 

 however, and then the spore presents the usual cruciate aspect. True 

 cases of tripartite spores are to be found, however, where the longi- 

 tudinal division of the lower cell has actually taken place in a direc- 

 tion at right angles to that of the upper one (Fig. 13). The contents 

 of the tetraspores do not differ very markedly from those of the other 

 cells, except that they are more highly granular. Fully adult spores 

 from fresh specimens are usually of a brownish color, and measure ou 

 the average 45.5 X 28 ,u. Some apparently mature ones were much 

 smaller, being only 25 X 18 fi. The curious case of distortion of the 

 tetraspores where they were so enormously elongated has already been 

 noted; they measured about SO fjc long by 15-20 /ut broad. The tetra- 

 spores make their way out by the breaking away of the outer cellulose 

 skin, which becomes very weak as the frond increases in age, and may 

 then be easily ruptured by slight pressure. Attempts were made to 

 germinate the tetraspores, but all proved unsuccessful. It may have 

 been that the conditions were unfavorable, or perhaps that the tetra- 

 spores rest some time before germinating 



Besides the tetraspores, no one, so far as I am aware, has ever givea 

 an account of the reproductive organs of C/i9reocolax Pubjsiphonice.. 

 When it was found that the non -sexual reproduction of C. Pohpi- 

 phonice was by means of tetraspores, this alga could be classed with 

 much more certainty among the Florideaj, and it was reasonable to 

 suppose that cystocarps might be found on further search. It was, 

 indeed, with this possibility in view that I was led to investigate 

 C. Polysiphoni(E. In all of the material collected during the fall 

 and early winter of 1890, nothing but the tetrasporic fruit was no- 

 ticed. Some specimens obtained at Nahant, on December 11th, 

 proved more interesting. In a few of the fronds, structures were 

 found which at once appeared could be nothing else than cystocarps. 

 These observations were corroborated later, and more cystocarpic 

 material was procured, which enabled me to make out definitely the 

 structure of the fruit, and to some degree also its development. It 

 was not until much later that the trichogynes were first seen, and as 

 it was not possible to trace out the com|)lete course of development 

 from the trichogyne to the ripe cystocarp, it will be best to begm 

 with a description of the latter. 



