20 S etc hell. — An Examination of the Species 
running through it in all directions. The hyphae are like the 
hyphae of the other species. 
The large sori (150 /x to 300 /x in diameter) are arranged 
in a single row in each cylindrical chamber, the diameter of 
the sorus and the diameter of the chamber being very nearly 
equal. Sometimes the whole row of sori (8 or 10 in number) 
coalesce into one long gigantic sorus. The sori are attached 
to the sides of the chamber and are, as it were, suspended 
in it, by loose strands of hyphae, radiating from all portions 
of the periphery (Fig. 75). 
The structure of the sorus. is entirely different from that of 
any other species which I have had the opportunity of 
examining. The central portion is filled with a dense mass 
of very fine hyphae, closely intertwined. Around this is a 
variable number (3 to 8) of layers of spores loosely placed. 
Finally on the outside there is a conspicuous cortex of large, 
dark-brown cells (Fig. 75). 
The hyphae of the central part are only 1 /x to 2 /x in 
diameter, very closely and intricately interwoven, and fill up 
one-third to nearly one-half of the interior of the sorus. 
They are indistinct, as if their walls were slightly gelatinized. 
The spores are very loosely compacted together, spherical 
in shape, and 8 /-x to 12 /x in diameter. They are light-brown, 
thin-walled, with the usual contents. 
The cortical cells are different in shape from those of any 
other species. In a cross-section of the sorus they are 
generally heart-shaped (Fig. 76). As solid bodies they 
resemble the crowns and upper parts of molar teeth. A 
tangential view is shown in Fig. 77. The dimensions in cross- 
section are 12 to 16 /x by 8 /x to 12/01. 
The details of the development of the sorus have not been 
carefully studied. The hyphae form first a loose ball, as in 
all the other species. The outer hyphae seem to have a 
slight radial arrangement, and their cells become swollen. 
The outermost cell is always the largest and finally becomes 
a cortical cell ; those farther in become spores, and the central 
confused mass of hyphae remains almost unchanged. There 
