76 BOTANICAL RESULTS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 



The following details of the minute structure were published in the Report of the 

 National Antarctic Expedition (loc. cit.) : 



The lamina has a monostromatic cortex, or outer layer, composed of quadratic thin- 

 walled cells with granular contents. Beneath this is a subcortical tissue consisting of 

 about six layers of larger cells, rounded or oblong, lengthened parallel to the axis of the 

 frond. And interior to this is the characteristic medulla, composed of some nine or ten 

 rows of closely juxtaposed, narrow, elongated, and comparatively thick- walled cells, 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 dis- 

 tinguishable. Compare fig. 6 and its description. 



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

 of hyphse, chiefly longitudinal (fig. 7) 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 outer cortex lies beneath 

 a distinct superficial cuticle, and consists of three or four rows of small quadrate 

 cells arranged in radiating lines, which, passing inwards, gradually change into a 

 pluri-stromatic subcortex of large round and oblong cells, which in turn merges 

 into the medulla. 



The structure of the holdfasts, or organs of attachment, rather resembles that of 

 the stipes, but the strata are less definitely marked. There is a dense medullary mass 

 of hyphse, without any trumpet-hyphse.. The outer cortex is composed of small, 

 dense-coloured quadrate cells which, traced radially inwards, change gradually into 

 larger and larger thin-walled subcortical cells, which in turn undergo transition into 

 the medulla. 



As regards the systematic position of the plant, we had no doubt in our minds at 

 first that it was conspecific with the type of our Lessonia grandifolia from Cape Adare. 

 For the Scotia specimens, though fragmentary, suggested a striking external resemblance 

 to the type. But later, when we had made a more careful comparison of the microscopic 

 structure, we found ourselves compelled to separate the Scotia plant off as a proper 

 species Lessonia simulans. 



The most obvious difference between L. simulans and L. grandifolia is found in 

 the medulla of the lamina. In L. simulans the medulla is a very pale-brown tissue of 

 close-set elongated cells, with very few ensheathed trumpet-hypbse among them ; whereas 

 in L. grandifolia the medulla is colourless and composed of hyphse mostly longitudinal, 

 laxly juxtaposed, separated from one another by one or two times their diameter, and 

 interspersed with numerous ensheathed trumpet-hyphse disposed in a wide median band. 

 Another point of difference is found in the cortex, which in L. simulans is monostro- 

 matic, and composed of quadrate cells with granular contents. In L. grandifolia the 

 cortex is composed of short vertical crowded rows of small brown cells. 



But whether L. simulans differs essentially from L. grandifolia in habit or external 

 characters, we are unable to say ; for the material of the former was incomplete. 



