396 Mottier. — Contributions to the 
cells over the apex of the columella multiplied by tangential 
divisions, so that this region consisted of a mass of archesporial 
cells (Figs. 4 and 5), instead of a single layer, as in Anthoceros. 
Transverse sections reveal the same structures as those seen 
in longitudinal sections. Fig. 6 , a , b , and c, represent cross- 
sections of a sporogonium of about the same stage in develop- 
ment as Fig. 5, taken at a-a , b-b , and c-c respectively : Figs. 7 
to 14, inclusive, represent successive cross-sections, including all 
of a similar sporogonium above the foot. In Fig. 7 the centre 
is occupied by four cells, the columella, surrounded by a peri- 
pheral row. In Figs. 8, 9, 10 the archesporium is seen, in 
addition to the other two regions. There can be no question 
as to its origin. These sections are not unlike Fig. 1 5, save in 
the latter the cell-divisions take place with diagrammatic regu- 
larity. In Fig. 11 the section passes through the extreme tip 
of the columella, of which three cells are shown. Figs. 12, 13, 
14 embrace the remainder of the sporogonium above the 
columella. 
The sporogonium of Notothylas undergoes intercalary growth, 
just as in Anthoceros , and the archesporium and columella 
extend quite to the foot (Fig. 19). In one case observed 
(Fig. 19), the cells of the foot were quite regular ; they had not 
grown into the irregular tubes which is almost invariably the 
case. The intercalary growth is, of course, of comparatively 
short duration, but as long as it lasts there cannot properly be 
said to be a stalk in the sense of that term as used in the 
Jungermannieae. It is only when the capsule is mature that 
the cells immediately connecting foot and capsule elongate 
and finally break away from the foot., thereby severing all 
organic connexion with the latter. 
As is stated by Leitgeb 1 , the size of the sporogonium is no 
proof of its age. Not infrequently does one find on the same 
thallus small sporogonia with others very much larger. Many 
of these smaller sporogonia, which appear under the dissecting- 
microscope to be younger stages, have in their apex spore- 
1 Loc. cit. 
