Igl6 ] ROE—CO.XCEPTACLE IN FUCUS 235 



Bower pays considerable attention to the "central column." 

 "The change of ihe substance filling the cavity has advanced so far that 

 the unaltered portion immediately surrounding the remnants of the initial 

 cell forms a central column of irregular outline. This stretches from the basal 

 cell to the neck of the coneeptacle, and is connected with the walls of the con- 

 ceptacle by thin strings, which, like itself, have remained as yet unchanged" 

 (p. 40). 



He offers as an explanation that there are three substances present: 

 (a) a swollen form of cell wall, which is not true cellulose, but is 

 similar to the central portion of older cell walls of the tissue of the 

 larger tangles; (b) a substance coincident with mucilage; and (V) 

 a substance akin to cuticle. Later the connecting strings are 

 ruptured. 



In conclusion (p. 47), Bower states that 



"In all the cases described, the formation of the coneeptacle is preceded by 

 the decay of one or more calls which occupy a central position with regard to 

 the changes which follow. The number of the cells thus removed is various, 



and the manner of their distribution is not constant A point which is 



not so obvious, but which appears of similar constancy, is that the cell or cells 

 which decay are in all cases members of a linear series. It depends upon the 

 activity of division, in a direction tangential to the surface of the thallus, how 

 this series is characterized; whether, as in Fucus, where the division is slow 

 and even ceases, the apical cell of the series hangs behind the surrounding 

 tissue; or whether, as in Himanthalia, where the division is often repeated, the 

 series is elongated, and, protruding beyond the surface of the thallus, is called 

 a hair"; and (p. 48): "This variation in activity of tangential division 

 accounts for the want of uniformity in number of the cells thrown off in differ- 

 ent species, and even in the same species The differences in mode of 



development (in the early stages at least) depend upon the difference in activity 

 of tangential division of the cells of the central series." 



Bower regards the hairpit as an incomplete coneeptacle, but 

 that "The homology of the two structures is so clearly proved that 

 I shall be justified in proposing .... the name 'neutral con- 

 eeptacle' (p. 44). I think it is important to convey at once the 

 relation which appears to exist between them and the true 

 coneeptacle." 



Yaliante in 1883 (29) describes the method of development 

 for Cystoscira and related genera. Primordia develop in the apical 

 grooves of ultimate branches, a hollow being formed just as in 



