144 University of California Fuhlications. [botaxv 



the cross section that the adventitious frondnles, arising from the 

 surface or edge of the frond, develop from these groups of 

 isolated cells. It may be that these fronds break off occasionally 

 and form new individuals, as their attachment is very slight. 

 The cell groups are doubtless forced outwards by their own ra]>id 

 growth and division, which is usually in the planes at right 

 angles to the surface and l)y the outward pressure of the growing 

 hyi)lup in the medulla and cortex immediately surrounding the 

 capsule. 



The algal cells are 6-13 m high and 4-5 yt-t wide. They 

 are from oblong to oval in shape, with the longest diameter 

 at right angles to the surface of the frond, so that the two cell 

 layers appear much like the palisade cells of the higher plants: 

 In the superficial view the cells seem scattered about without any 

 special order, and they appear almost quadrangular with medium 

 spaces between them. 



The medulla is about one-third the entire thickness of the 

 frond, that is, 20-50 /* thick. It is composed of innumerable 

 fine mycelial filaments interwoven closely in all directions, 

 though the majority are parallel to the surfaces. A gelatinous 

 coat surrounds each filament and these coats coalesce, filling in 

 all the interspaces. The filaments are cylindrical, hyaline and 

 much finer than those projecting into the cortex, being scarcely 

 1 ^ in diameter. The walls are thick and the contents granular. 



The perithecia appear on the surface of the frond as blackish 

 spherical swellings. They measure in superficial diameter 364- 

 520 ^ and are usually spherical and mammillate, but are 

 sometimes fiattened oval. Each perithecium consists of a large 

 rounded cavity of aliout the diameter of the normal frond, 

 surrounded by a thick wall. In the cross section (Cf. Fig. 3, 

 PI. 15) the wall is seen to be deeply pigmented about the ostiole, 

 and also on the side of the cavity, opposite the ostiole, that is, 

 the basal wall. The cavity is lined by a colorless thin pseudo- 

 parenchyniatous layer, from which the club-shaped asci originate, 

 and project towards the center. The surface of the perithecium 

 is the outer cortical layer of the frond which is somewhat modi- 

 fied by the growth and expansion of the interior tissues. The 

 algal layer is also consideral)ly modified. There are numerous 



