F. Børgesen: Phæophyceæ of the Danish W. Indies. 39 



that it is composed of numerous rows of cells radiating flabelli- 

 form out from the margin ; along this we find a series of large 

 cells and these divide themselves gradually by longitudinal and 

 transverse walls, each in this way giving rise to 2 — 4 rows of 

 cells. In a transverse section (Fig. 24 a) we find that the thallus 

 consists of a medullary layer of large cells with dark brown 

 contents in the middle, and one or two, on the upper side occasion- 

 ally even three, large flat cells; at the surface on both sides an 

 epidermal layer of small cells. The large flat cells nearest the 

 periphery are most often, in any case in older parts of the 

 thallus, divided by vertical, secondary walls into two to four 

 cells, more seldom horizontal walls also occur. 



A transverse section of the edge (Fig. 24 c) shows the develop- 

 ment of the thallus. First by a vertical wall a large cell is cut 

 off from the topcell and at the new cells upper and under side 

 two flat cells are formed from which the epidermal layer has it 

 origin, the cells on the upper side being gradually divided into 

 4 — 6 small cells those below most often only in two or not at 

 all (comp. Fig. 24 a). From the large cell in the middle of the 

 thallus one, two or sometimes even three flat cells are cut off on 

 the upper side, one or sometimes two from its under side. While 

 these cells on the side below most often are undivided, sometimes 

 though divided by a vertical wall into two cells, those on the upper 

 side are somewhat more divided especially the uppermost cells. 

 The large cells in the middle are sometimes also divided by vertical 

 walls into two cells (the two cells to the right in Fig. 24 a). 



The rhizoids are outgrowths from the epidermal cells below. 

 Upon the upper side of the thallus here and there scattered 

 groups of hairs occur ; the hairs have their origin from epidermal 

 cells (Fig. 24 d). 



Unfortunately all my material was sterile. 



As will be clear from this description, my plant seems to 

 agree with that of Sauvageau, only that it is sterile, and this 

 I have also confirmed by examination of original material from 

 the Canary Isles which Prof. Sauvageau has most kindly sent 

 to me. 



In my preliminary paper I have pointed out that Raljsia 

 ceylanica Harv. most probably belongs to this species. And the 

 same I think is also the case with Zonaria parvula Grev. var. 

 duplex Heydrich. 



In the Danish West Indies Aglaozonia canariensis was found 

 on very exposed coast incrusting the rocks at about high water 



