Olson : OBSERVATIONS ON GIGARTINA. 157 



TOWS extending vertically through the holdfast. This is more 

 apparent outside the region of the pit than within. In passing 

 from the holdfast proper to the stipe the character of the cells is 

 seen to change, the outline becomes rounded, the cells smaller 

 and the arrangement very irregular (Fig. lo c, PI. 13). On 

 the upper side of this zone the cells become elongated and soon 

 merge into the structure of the stipe (Fig. 10 d, PI. 13). At 

 the side, in the region where the surface of the holdfast passes 

 to the surface of the stipe, an interesting curvature of the rows of 

 cells of the holdfast is noticed (Fig. 10 e, PI. 13). The upper 

 cells of the holdfast gradually become smaller and merge into 

 the outer cells of the stipe, so that at the periphery there is not 

 so marked a change in the character of the cells as in the 

 center. The central elongated cells of this stipe extend farther 

 into the holdfast in the center than at the periphery of the stipe 

 region. This is to be expected from the outline of the pits 

 from which the stipe has been removed, and an examination of 

 these pits under high power reveals the fact that none of the 

 elongated stipe cells are present in the scar, showing that the 

 separation zone when a stipe is pulled from a holdfast is at the 

 region shown in Fig. 10, PL 13 at c, and curves upward at the 

 sides, thereby forming the pit-like scar. 



In many sections of stipe and holdfast the elongated cells are 

 seen to extend much farther down than in the section of Ficr. 

 10, PI. 13, so that only one or two layers of holdfast cells lie 

 between them and the lower surface. 



In a few sections an interesting development of outgrowths on 

 the lower surface was noticed. These occur below the stipe 

 region and show the same cellular structure as the holdfast 

 proper. They are apparently rhizoid-like growths (Fig. 10, 



PI. 13)- 



The sections used were placed in an alcoholic solution of 

 fuchsin for a few moments, fhen washed with alcohol and 

 mounted in gl^xerine jelly. The stain failed to bring out any 

 cell contents and to all appearances the cells are empty. 



Stifc and Lamina. — The structure of the stipe and lamina is 

 very similar, the chief difference being that in the former the 

 cells are of somewhat smaller diameter. 



The upright portion of the plant may be divided, anatomic- 

 ally, into two fairly distinct portions : the pith, consisting 

 of the larger, apparently empty cells and the cortex, of smaller 



