120 
DICTYOTACEiE. — Hydroclathrtjs. 
iv. 
and having thin walls. The outer stratum in which ^lie colour resides is very thin, 
composed of exceedingly minute cells, with square ends, but whose exact shape I 
could not well determine. Dr. Montagne, in his splendid work on Algerian Algae, 
says that they are parallelipipeds, placed, with their smaller ends to the circumfer- 
ence. With the views respecting this species entertained by Dr. Montagne and 
expressed in that work I fully concur, and now proceed to describe this curious 
vegetable in detail. 
1. Hydroclathrtjs cancellatus , Bory. — Mont. Alg. Algier. p. 36. Asperococcus 
clathratus , J. Ag. Sp>. Alg ., vol. 1 , p. 75. Encoelium clathratum , Ag. — Kiitz. Sp. Alg. 
p. 552. Halodictyon cancellation , Kiitz. Phyc. Gen. p. 338. (Tab. IX. A.) 
Hab. Subtropical. On rocks, etc., in tide pools near low-water mark. Annual. 
Sand Key, Florida, abundant in February. W. H. IP. (v. v.) 
Fronds of irregular form, oblong or sinuous, two to three inches in length and 
about an inch high, heaped together in wide-spreading patches, adhering to the 
rocks by the lower surface, and to each other by their sides. The young fronds, 
in the earliest stage at which they were found, are pierced by rounded holes, of 
small size and somewhat pressed together. As the membrane expands, the original 
holes expand also, and grow wider, and new holes are formed in the interspaces, 
until the whole membranous wall of the bag-like body is converted into a 
delicate, lace-like network. The margin round each hole is strongly involute, which 
gives the appearance of a thickened rim, when the membrane is viewed vertically. 
The substance is thick, crisp to the touch at first, but very fragile, and it soon 
changes colour and loses rigidity on exposure to the air. The surface-cells are 
exceedingly minute, filled with colouring matter ; those that compose the thickness 
of the membrane are of large size, hexagonal, with thin walls and full of watery 
juice. No fructification was observed on my specimens. The colour when 
growing was a very pale, yellowish- olive, somewhat ochraceous. This rapidly 
changes, and the plant becomes dark brown in a dried state. 
Our figure gives a tolerable idea of the Sand Key plant, as to size of individual 
fronds and mode of composition of the patches : but I have failed in making it suffi- 
ciently lace-like, and in giving the effect of depth to the holes which pierce it in every 
direction. I have some doubts whether all the plants known under the name H. 
cancellatus are identical. The beautiful figure in the great French work on Egypt, 
would not at all answer any specimen of the Sand Key plant which fell under 
my notice. But it must be borne in mind that my specimens were gathered early 
in the season, and were comparatively young ; and, therefore, it is possible that 
later in the year they might have put on a very different aspect. If all the 
clathrate Algae referred to this place by botanists belong to the present species, it 
has a wide range ; being found through the warmer parts of the Atlantic at both 
sides ; in the Mediterranean ; the Red Sea ; on the shores of the Mauritius, and 
