274 CATALOGUE OF THE MARINE ALG^ 



Jj. digitata, var. stenophylla. Harv. Pliyc. Brit., t. 

 338. Atlas, PI. ViL, fig. 25. 



On rocks from half-tide level to beyond low-water mark. 

 Common. 



The plant here alluded to was first described by the Rev. 

 Charles Clouston, in an Appendix to Anderson's " Guide to the 

 Highlands and Islands of Scotland." It has also been figured 

 by Professor Harvey {loc. cit.), but I am not aware that any 

 account of its minute structure has ever been published.* Dr. 

 Harvey adds nothing to Mr. Clouston's very graphic descrip- 

 tion of the external characters of the plant, but expresses 

 a belief that it is specifically distinct from L. digitata (Clous- 

 toni). That such is truly the case, I think no one who 

 examines the plant carefully on the sea-shore, and under the 

 microscope, will be disposed to doubt. 



The most important characters of the two plants may be 

 briefly stated as follows : — 



L. Cloustoni.— The stein is cylindrical, rigid, and rough, with 

 longitudinally arranged tubercles or rugae. A transverse section 

 shows a well-defined circular (or nearly circular) pith, and a 

 deeply coloured cortex, which is easily separable from the subja- 

 cent cellular tissues. These 'are arranged in more or less evident 

 concentric layers, each ring of which corresponds (according to M. 

 Le Jolis) to a year's growth of the stem (tu'cZe PI. XV., figs. 5, G, 

 8). Under the microscope the cortical layer is seen to be sepa- 

 rated from the cellular tissue of the stem by a series of canals — 

 vasa mucifera of Kutzing. The root-fibres or processes form a 

 conical mass, and are arranged in regular vertical series (fig. 7). 

 The frond is very much shorter than the stem. It contains a 

 dense central layer of elongated anastomosing cells, connected 

 with the epidermis on each side by a laxly composed tissue, of 

 which the cells are somewhat quadrilateral in outline. In this 



* Since the above was -written, I liave been furnished, through the kindness of Dr. Har- 

 vey, with a paper on the genus Laminaria, by M. Auguste le Jolis, of Cherbourg, In tliis 

 memoir the distinctive characters of the species in question are fully elucidated, and I find 

 no important difference between the results of my own ndependent observation and those 

 of M. le Jolis. I retain, however, in this place a somewhat condensed abstract of a paper 

 which I had written before, being aware that the subject was pre-occupied, adopting at the 

 same time M. le Jolis' specific names of flex icav Us and Clouston i. 



