86 



extending from the compact ventral tissue to above the middle of 

 the uppermost green cells, united at their upper ends and some- 

 times at various points along their length; compact ventral 

 tissue mostly eight to ten cells thick, composed of uniform paren- 

 chyma without oil-bodies: inflorescence (so far as known) 

 dioicous, the antheridia not seen: spores dark brown to almost 

 black, becoming very opaque with age, more or less angular, 

 1 10-130 )u in diameter, with a narrow, irregular and often in- 

 terrupted wing-margin, 4 ^t or less in width, spherical face covered 

 over with a fairly regular reticulum formed by low ridges 3 fx 

 or less in height, the meshes mostly 10-15 m in diameter, plane 

 faces with lower ridges, usually irregular but sometimes forming 

 a more or less distinct reticulum. [Fig. i.] 



On soil, Santa Ana, 900 m. alt., June 25, 1915, Cook & Gilbert 

 1 48 1. 



The peculiar bands of thickening which are found in the walls 

 of the green cells represent a feature which has not before been 

 noted in the Marchantiales. In a section cut parallel with the 

 surface of the thallus (Fig. i, D) these bands are especially con- 

 spicuous. They appear in the form of minute circular structures 

 situated in the walls common to two cells and projecting into the 

 cavities, this appearance being due to the fact that the thicken- 

 ings deposited by one cell correspond with those deposited by 

 its neighbors. In most cases each cell is octagonal in section and 

 is bounded by four other cells alternating with four air-canals. 

 At its periphery it shows normally eight thickenings, two for 

 each bounding cell. The thickenings are usually distinct and 

 definitely two in number, but they sometimes have vague out- 

 lines and may be increased to three. In a section cut at right 

 angles to the surface of the thallus (Fig. i, E) the true form of 

 the thickenings becomes evident. They now appear as parallel 

 bands, running longitudinally with respect to the rows of green 

 cells. Each pair of bands begins at or near the lower end of a 

 row and extends upward to the cells just beneath the epidermis. 

 A short distance above the middle of these cells the two bands 

 coalesce and form a narrow arch. During their course they 

 sometimes unite here and there but are usually quite free from 

 each other. 



Although thickened walls have not before been observed in the 



