Humphrey : OBSERVATIONS ON Gigartina exasperata HARV. 605 



In the material at hand the writer was unable to secure any 

 sections showing tetraspores. 



The development of the cystocarp, however, was quite clearly 

 brought out. As the proliferation advances in its development 

 there arises an irregular cellular formation of gonimoblast fila- 

 ments and sterile tissue in the interior of which groups of 

 branched filaments develop the carpospores. This entire for- 

 mation is surrounded by a definite area of cells forming the 

 cystocarpic wall. As the cystocarp advances towards maturity 

 a perforation occurs through the breaking down and gradual 

 dissolution of certain cells, thus furnishing the mature spores an 

 avenue of escape (PL 42, Fig. u). The tissue of the pro- 

 liferation surrounding the spore cavity is similar to that of the 

 lamina proper, except that the cells are more compactly ar- 

 ranged. 



Sections of this tissue were treated with Delafield's haema- 

 toxylin which proved to be a good nuclear stain revealing in 

 several cells well-marked nuclei. (PI. 42, Fig. 12.) 



Several sections were made in order to determine the struc- 

 ture and characteristics of the mature cystocarp. PL 42, 

 Fig. 13, represents such a cystocarp showing the spores ar- 

 ranged in groups surrounded by apparently empty filamentous 

 cells, thus forming a compound cystocarp. Previous to the 

 maturity of the spores they are all attached to the gonimoblastic 

 filaments of which they were originally a part. They are evi- 

 dently attached by means of protoplasmic threads, though no 

 evidence of pits occurred. (PL 42, Fig. 15.) The carpo- 

 spores, when mature, measure from 10 to 12 /* along one di- 

 ameter and u to 13 fj. along the other, while the cystocarp 

 measures from two to three mm. in diameter through the con- 

 ceptacle. 



BIBLIOGRAPHY. 



Harvey, W. H. Notice of a collection of algae made on the north- 

 west coast of North America, chiefly at Vancouver's Island, by 

 David Lyall in 1859-61. (Jour. Proc. of Linn. Soc. 6: 172, 

 173. 1862. 



Cocks, J. Observations on the growth and time of appearance of 

 some of the marine algae. Jour. Proc. of Linn. Soc. 4: 101- 

 106. 1860. 



