50 VALONIACE^. 



moderately high magnifying power it appears to be transversely striate. The primordial 

 sac readily separates from the outer cell-wall. 



This plant was first noticed in the Mediterranean Sea, where it grows in the fissures 

 of littoral rocks in many places. It occurs also in Brazil, from whence I possess a 

 specimen ; and is found generally throughout the West Indian Islands. Our Key West 

 specimens are rarely more than two inches high and about three in breadth. The 

 largest specimen I possess was given me by the late Mr. Menzies, as having been 

 dredged in twenty fathoms in the Gulf of Mexico. This specimen measures six inches 

 across, and its venation ofiers some peculiarities ; which perhaps may lead to its specific 

 separation. In our Key West plants the seriated cells of the principal veins stand apart 

 from each other, or are in single file, leaving wedgeshaped spaces between. In Mr. 

 Menzies' specimen the principal veins are partly unicellular, partly formed of several 

 parallel, closely placed cells, without interspaces. The structure is easily seen, but 

 difficult to describe in intelligible language. Should subsequent observations establish 

 this plant as a species, it may be called A. Menziesii. 



Plate XLIV. A. Fig. 1. Anadyomene flahellata^ full grown ; and Fig. 2, a young 

 plant ; the natural size. Fig. 3 represents Fig. 2, magnijied, to show the structure of 

 the frond. 



V. DICTYOSPH^RIA. Due. 



Boot consisting of a few grasping processes. Frond, a decumbent, amorphous mem- 

 brane composed of a single series of vesicated, sub-globose, tough-coated cells, filled 

 with green, fluid endochrome. Fructijication unknown. 



The plant for which this genus was defined by Decaisne was formerly referred to 

 Valonia, to which no doubt it is closely allied, but from which it differs by the greater 

 lateral coherence of the cells which compose the frond, and also by the structure of these 

 cells. It is of common occurrence throughout the tropics of both hemispheres. On the 

 coast of Australia a second species is equally common, difieringfrom D.favulosa in the 

 frond being never vesicated, and in the component cells being very much smaller, the 

 surface flatter, and the frond having a silky lustre. This I have elsewhere described 

 under the name D. sericea. 



1. DictyospHjERIA favulosa, Dne.; frond at first globose and hollow, afterwards 

 irregularly torn, expanded ; the vesicated cells globoso-hexagonal, convex, and very 

 prominent. Dne. An. Sc. N^at. Ser. 2. vol. 17, p. 328. Kiitz. Sp. Alg. p. 512. 

 Valonia favulosa, Ag. Sp. Alg. 1. p. 432. (Tab. XLIV. B). 



