Marchantiales. 
97 
aggregation of the antheridia into groups, and this is very 
pronounced in R. nntcins, in which these organs are developed in 
two or three rows on a long receptacle, forming a ridge with a 
groove on either side and arched over by the neighbouring tissue of 
the thallus (Fig. 6). 
In Tessellina (Fig. 7), the air-chambers are arranged in a single 
Fig. 7. Tesselina pyramidata. A, a male plant, x 2 ; B, a female plant, 
x 2; C, transverse section of a male plant, showing two antheridia. 
series, and each opens by a pore which is raised above the surface 
of the thallus and surrounded by five or six cells with strongly 
thickened radial walls. The ventral scales arise in two independent 
rows, as in the higher Marchantiales. The antheridia are in groups, 
marked by tufts of hairs among which arise the cylindrical ostioles 
of the antheridial chambers. In the female plant, each archegonium 
becomes surrounded by a conspicuous green conical outgrowth 
containing air-chambers. As was shown by Leitgeb, the capsule 
contains rounded sterile cells, but since these lie just within the 
capsule-wall, it is doubtful whether they can be regarded as sterile 
archesporial cells. Leitgeb 1 thought these sterile cells represented 
1 Untersuchungen, IV., p. 45. 
