602 MINNESOTA BOTANICAL STUDIES. 
Floldfast: The holdfast is a disc-shaped organ, exhibiting 
considerable variation in size. Inthe 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. Pl. 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 contents. 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 (Pl. 42, Fig. 2, 6) 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. 
Stzpe.—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- 
