DICTYOTACE^.— Hydeoclathrus. 119 



SPECIES OF DOUBTFUL AFFINITY. 



3. AsPEROCOCCUS intr'icatus, J. Ag., " frond tubular, branched, sub-hemispheri- 

 cally expanded, subrepent ; branches intricate, gradually attenuated, decompound- 

 dichotomous ; the apices forked." /. Ag. Sp. Alg. vol. 1, p. 77. 



Hab. Tropical. At Vera Cruz, Mexico. (Liebman). 



I am not acquainted with this plant, which scarcely seems to fall naturally 

 under this jrenus. 



XL HYDROCLATHRUS, Bory. 



Frond membranaceous, convex, hemispherical, bag-shaped, regularly pierced with 

 orbicular holes, which gradually dilate more and more, until the plant becomes a 

 clathrate net, eventually mishapen and ruptured. Margin of the apertures involute, 

 " Spores minute, globose, collected into dot-like, scattered, innate sori, accompanied 

 by club-shaped, jointed filaments." {Mont.) 



This is a very remarkable plant, and of so peculiar a habit, as well as distinct struc- 

 ture, that I can hardly imagine any person who has had an opportunity of seeing 

 it alive on its native rocks, placing it in the same genus with Asperococcus shiuosus; 

 although my valued friend Prof J. Agardh even doubts its specific diversity from 

 that species. I must suppose that Prof Agardh has formed his judgment from an 

 examination of dried specimens, which are so wholly unlike the living plant in 

 appearance, and can be so imperfectly examined when remoistened, that a satisfac- 

 toiy opinion can scarcely be formed from them. I regret that the microscope 

 which I had with me at Key West was not of sufficient power to enable me to 

 make out the anatomical structure perfectly, and the plant decomposed so 

 rapidly that it was difficult to obtain good slices of the membrane sufficiently 

 thin for examination. When fresh from the sea, the frond was quite crisp, and 

 could readily have been cut, but my specimens (collected at Sand Key) had to be 

 brought a long way in an open boat, under a hot sun ; and although every care was 

 taken to keep them cool, and though they were brought in buckets of water, decom- 

 position had commenced long before they reached Key AVest, and then, in the 

 attempt to save from destruction a large gathering of other Algaa, the fruit of the 

 same excursion, only very imperfect notes could be made on the present curious 

 plant. Such sections as I was able to make through the membrane showed me that 

 it was composed of several rows of cells ; the inner rows, occupying almost the 

 whole thickness, being formed of large, colourless cells, filled with fluid, distended, 



