Notes on the Morphology of the Fucacece. 39 



and of a medullary portion. The cortical portion is made up of parallel 

 filaments running perpendicularly to the surface of the thallus. These 

 filaments are very closely packed and regularly septate, causing the cortical 

 portion to present the appearance of a compact mass of parallel rows of 

 cells. As the filaments pass down to the medullary portion, they cease to 

 run parallel to each other, and branch out irregularly in all directions, 

 anastomosing more freely, while the individual cells expand in diameter, 

 and the septa are further apart. Thus the medullary portion is made 

 up of a mass of branching and anastomosing filaments running in every 

 direction, forming a tissue which is looser than that of the cortical portion. 

 The conceptacles extend to the same depth as the cortical portion, their 

 bases being surrounded by filaments of the medullary portion. The 

 material at my disposal consisting only of mature parts of the fronds, 

 I have been unable to investigate either the mode of apical growth or 

 the mode of development of the conceptacles. 



The male conceptacles are of the ordinary Fucaceous type, and contain 

 antheridia borne on branching filaments (plate XII., fig. ij. 



The female conceptacles (plate XII., fig. 2) contain oogonia, the contents 

 of which divide into four oospheres in the following manner : the proto- 

 plasm of the immature oogonium divides into three transversely, and the 

 middle portion then divides again into two longitudinally. This mode of 

 division was first observed by Kiitzing, who, as has been already noted, 

 regarded the four resulting oospheres as tetraspores. A peculiarity about 

 the oogonia is ( that, while many of them are developed in the usual 

 manner from the lining cells of the wall of the conceptacle, others are 

 borne laterally on branching filaments (plate XII., fig. 3). These filaments 

 are longer, and their component cells are larger, than in the case of the 

 antheridia-bearing filaments. There are only a very few sterile filaments 

 on either the male or the female conceptacles, and these occur chiefly at 

 the mouth of the ostiole. FRANCES G. WHITTING. 



(For explanation of figures on plate XII. see p. 46.) 



