292 MINNESOTA BOTANICAL STUDIES. 



finer and thinner and of the same dark red color. The second- 

 ary laminae not infrequently arise from the surface instead of 

 the margin of the primary frond (Jig. 2). A third series of 

 laminae rising from the margin of the secondary laminae was 

 common, but a series of four as in fig. 3 was comparatively 

 rare. A plant often reaches twenty-five and thirty centimeters 

 from stipe to margin of outermost lamina. The dried specimen 

 does not adhere well to the paper. 



MINUTE STRUCTURE. 



The material used consisted chiefly of free-hand razor sec- 

 tions of fresh plants gathered in the summer of 1902. The 

 mature cystocarps were studied from formalin material collected 

 in December, 1901, at the same point. 



1. Holdfast. The holdfast is comparatively small and fits 

 like a sucker to the surface of a flat rock or curves over a pro- 

 jection or barnacle (figs. 4., 5). A thick layer of gelatine lying 

 close to the rock fits into all uneven places and takes the im- 

 pression of the rock (fig. 6). Above this, thick at the center 

 and thinner at the margin, lies a layer of cortical cells covered 

 by an epidermal layer several cells in thickness (fig. 7). Several 

 holdfasts were sectioned in which a second cortical and epi- 

 dermal layer appeared to have grown out over the first, so that 

 a layer of gelatine lay within the tissues of the holdfast. 



2. Stipe. The main stipe was about five millimeters in 

 length, cylindrical in form, becoming oval in cross section where 

 it passes into the lamina. The older stipes are thicker but not 

 longer than the younger ones. 



The epidermis consists of deeply colored, thick walled, some- 

 what rectangular cells arranged in several rows. The cells of 

 the true epidermis are rather larger than those of the subepi- 

 dermis. Dimensions, 6.5 to 16.5 mic. in length and 6.5 mic. in 

 width (Plate XLIV.,fig. 8}. 



The cortex is made up of large, clear, colorless cells. The 

 cells of the inner cortex are much larger than those of any other 

 part of the plant. Dimensions, diameter 16 to 50 mic. (Plate 

 XLIV.,fig. 9 ). 



In the center lie the long, narrow, thick-walled cells of the 

 pith strand. These run mainly longitudinally, very few running 

 transversely. Dimensions, diameter 20 mic. (Plate XL IV., 

 figs. 10, n). 



