MoLLET. — On the Structure of Hormosira billardieri. 321 



the proximal end of the node. At the distal end the central part of the 

 tissue conies to an abrupt termination, leaving the surrounding mass only 

 to pass on into the internode, where the parallel cells are comparatively few, 

 being replaced by those of irregular shape. 



Conceptades. — The conceptacles, containing the sexual organs, are scat- 

 tered over the surface of the internode, or, rather, in its outer tissues. The 

 conceptacles are flask-shaped, and about '03 inch in diameter. The tissue 

 lining them is of two distinct kinds ; that of the mouth and about one-sixth 

 of the depth of the cavity resembles, and is apparently a contmuation of, 

 the limiting tissue (PL XIII., fig. 4), but the remainder consists of cortical 

 tissue. These facts would lead to the supposition that the origin of these 

 conceptacles is the same as that of those in Fucus serratus ;* but on this 

 point I am not prepared to give a definite opinion. 



At some little distance within the mouth of the conceptacle (male and 

 female), viz., from the termination of the limiting tissue, and extending to 

 about an equal depth within the cavity, is to be found a collection of multi- 

 cellular hairs, which protrude for some distance out of the mouth of the 

 conceptacle. (PI. XIII., fig. 4.) These hairs are quite distinct from, and 

 have no resemblance to, the slender filaments hereafter mentioned. At the 

 base the length of the cells, of which these hairs are composed, is equal to 

 the diameter ; but as we trace the cells on towards the free end, we find 

 them gradually elongating till, at the extremity, their length is many times 

 that of their diameter. (PI. XIII., fig. 7.) 



In the female conceptacle (PI. XIII., fig. 4) the remaining surface is 

 densely covered with slender filaments, most of them extending nearly to 

 the centre of the cavity. The oogonia, irregularly scattered among these 

 paranemata, contain in the primitive stage yellow granular matter, which 

 slowly changes, as they increase in size, to a dark brown colour, and finally 

 divides to form four oospheres. (PI. XIII., figs. 4 and 8.) 



In the conceptacle containing the male organs of reproduction, the 

 slender filaments are wanting ; but their place is occupied by thick clusters 

 of branched hairs (PI. XIII., fig. 9), upon which are formed the antheridia. 

 The cell- walls of the latter are divided into two layers — an inner and an 

 outer ; the outer forming part of the branching hair. When the antheri- 

 dium is mature it escapes slowly from this outer cell-wall, and is then seen 

 to consist of the previously inner cell-wall filled with antherozoids. (PL 

 XIII., fig. 9.) 



Eeferring again to the oogonia, which I have not seen in a mature con- 

 dition, it may be well to state that they appear, when young, cylindrical; at 



* See F. 0. Bower, loc. cit. 



41 



