6 ANTONY GEPP AND ETHEL S. GEPP. 



calibus oblongis parenchymaticis in circa 6-7 series dispositis ; meduUaribus elongatis 

 angustis strictis 9-10 seriatis tubulos perpaucos subinfundibuliformes vagina e cellulis 

 parvulis composita vestitos foventibus. Caetera desunt (fig. 10). 



South Orkneys, Scotia Bay, near surface; April, 1904, leg. E. N. Rudmose Brown. 



A section of the lamina of this plant was figured in the Journal of Botany (loc. 

 cit.) as representing that of L. grandifolia. We had at the time no doubt that the 

 ' Scotia ' specimens which, though fragmentary, presented so striking an external 

 likeness to the type, were identical with it ; for such differences of structure as were 

 apparent seemed to be due to a different method of preservation. The ' Scotia ' 

 specimens were preserved in spirit, and exhibited a simpler and clearer cell-structure 

 than the ' Discovery ' material, which was preserved in formalin or merely dried. But, 

 after having made a more careful comparison of their microscopic structure, we are 

 convinced that the ' Scotia ' plant must be separated off" as a proper species, though the 

 material is insufficient to enable us to describe its complete habit. 



As regards the structure of the lamina, the cortex is monostromatic and composed 

 of quadratic thin- walled cells with granular contents (not rotunda te and densely 

 obscured, as erroneously figured in the Journal of Botany, loc. cit.). The subcortical 

 tissue consists of about six layers of larger cells, rounded or oblong, lengthened parallel 

 to the axis of the frond ; and the medulla is composed of some nine to ten rows of 

 narrow elongated cells, thick-walled, with a few ensheathed trumpet-hyphse scattered 

 among them. The medullary cells are sometimes filled with a pale brown mucilage, 

 and their limits are then barely distinguishable. 



In the stipes the medulla is the main tissue, and consists of a dense pale-brown 

 mass of hyphee, chiefly longitudinal (fig. 10) and straight, but here and there mingled 

 with interwoven hyphse. Scattered in the medulla are a very few trumpet-hyphse, 

 some with and some without a sheath of very small cells. The medulla externally 

 changes into a pluristromatic subcortex of large round and oblong cells which, passing 

 outwards in radial rows and subdividing, gradually changes to a cortex of three to four 

 rows of small quadrate cells, bounded by distinct cuticle. 



The structure of the holdfasts rather resembles that of the stipes, but the strata 

 are less definitely marked ; there is a dense medullary mass of hyphae which towards 

 the periphery change into lax, larger, thin-walled subcortical cells, and these in their 

 turn becoming smaller and smaller, pass into a cortex of small dense-coloured quadrate 

 cells. There are no trumpet-hyphse in the medulla of the holdfasts. 



The most obvious difference between L. sirnulans smd L. grandifolia ia found in the 

 medulla of the lamina. This in the former plant is a very pale-brown tissue of elongated 

 cells with very few ensheathed trumpet-hyphse. In L. grandifolia the medulla is 

 colourless and composed of hyphse mostly longitudinal, and laxly juxtaposed and 

 separated from one another by one to two times their diameter. The ensheathed 

 trumpet-hypha3 are numerous and obvious, and scattered along an irregular median line. 

 L. simulans diff"ers also in having a monostromatic cortex of quadrate cells. 



