602 MINNESOTA BOTANICAL STUDIES. 



Holdfast: The holdfast is a disc-shaped organ, exhibiting 

 considerable variation in size. In the case of a single frond the 

 holdfast is not much greater in diameter than the stipe immedi- 

 ately above. The under surface is smooth and somewhat flex- 

 ible, though in comparison with other tissues it shows greater 

 rigidity and strength. It is not unusual to find several fronds 

 attached to one common holdfast which, upon close examina- 

 tion, presents the appearance of a compound organ, in some 

 instances measuring nine mm. in diameter. 



The tissue of the holdfast is unlike that of any other part of 

 the plant. PI. 42, Fig. 2, represents a longitudinal section 

 through a portion of the holdfast showing distinctive areas from 

 the point of attachment to the substratum to the tissue of the 

 stipe. It was found that in removing the plant from its point 

 of attachment the cuticle was removed from the holdfast leaving 

 exposed those cells immediately adjacent, represented by (). 

 These cells appear to be somewhat irregular in outline, though 

 generally quadrilateral, and are characterized by their exceed- 

 ingly thick walls. Approaching the stipe these cells are slightly 

 modified and in conjunction with them are found rather long 

 somewhat egg-shaped cells, densely filled with coritents. These 

 cells, along with the others, are arranged approximately in rows 

 extending vertically through the holdfast. Protoplasmic connec- 

 tion exists between all cells and the cell arrangement is so com- 

 pact as to give great strength and rigidity to the tissue. These 

 cells (PI. 42, Fig. 2, d) are slightly modified and in conjunc- 

 tion with small, somewhat spherical cells closely attached and 

 densely filled with granular contents. Abutting upon this area 

 are the filamentous cells of the stipe, which are very similar to 

 those found elsewhere in the frond. 



Stipe. In the early stages of the plant's growth the stipe 

 is hardly to be distinguished from the lamina, but as the frond 

 reaches maturity the stipe becomes a well-marked organ of 

 deep red color. Immediately above the holdfast it is circular, 

 but as it gradually merges into the lamina it loses its charac- 

 teristic shape, becoming much expanded in one diameter and 

 thinner in the other. The stipe seldom exceeds a length of 20 

 mm., while the diameter varies from 2 to 5 mm. 



The stipe exhibits a structure similar to that of the lamina, 

 though in the former the cells possess shorter diameters and 

 the arrangement is more compact, thus affording greater rigid- 



