OF ARTS AND SCIENCES. 207 



and paraphyses. The September specimens show many details of the 

 development. The cells of the limiting layer elongate perpendicularly 

 to the surface of the frond until they are ten to twelve times as long 

 as broad. These elongated cells are slightly swollen at the tips, and 

 have granular brown contents and constitute the paraphyses. At ma- 

 turity, each is cut off from the cell whence it arose by a tangential 

 wall. The cuticula has been carried up and still covers the tips of 

 the paraphyses. After they are fully formed, the zoosporangia begin 

 to appear as small and broad swellings at the bases of the para[)hyses. 

 They generally arise from the basal cell of a paraphysis; at least, in 

 all cases where the point of origin could be distinctly determined this 

 was the case. 



In November specimens, the zoosporangia are well developed. The 

 cuticula has disappeared from over the tops of the paraphyses, and 

 the sori in consequence have taken on their characteristic velvety 

 appearance. The paraphyses themselves have a slightly thickened 

 tip. The zoosporangia are in the shape of obovoid sacs, about two 

 thirds the length of the paraphyses. The contents are of a light 

 yellow brown and are already divided up into spheres, the future 

 zoospores. The tip of the zoosporangium is noticeably thickened. 



Farlow* has called attention to the fact that the paraphyses are 

 destitute of the hyaline appendage of the paraphyses of the species of 

 Laminaria. Areschoug t has given measurements of both zoospo- 

 rangia and paraphyses. Kjellman | figures a zoosporangium and a 

 paraphysis ; but these drawings do not correspond exactly to the zoo- 

 sporangia and paraphyses of my specimens. Barber § has figured 

 and described the zoosporangia and paraphyses of Saccorhiza bulbosa, 

 which seem to agree very well with those of our plant. 



General Summary. 



I. The development of Saccorhiza dermatodea agrees in its general 

 features with what is known of the development of other Laminariece. 



II. The permanent holdfast is developed from a peculiar organ, 

 the rhizogen, which produces two successive whorls of hapteres, the 

 first organ of attachment or primitive disk being only a temporary 

 structure. 



* N. E. Alg., p. 96. 



+ Obs. Phyc, Part. III. p 12. 



t Spetsb. Thall., II., Taf. I. Fig. 8, 9, 1877. 



§ Annals of Botany, Vol. III. p. 58, PI. VI. Fig. 22. 



