204 
Lang. — On the Sporogonium of Notothylas. 
The characters of the gametophyte need only be briefly referred to for 
the purpose of systematic comparison and as introductory to the more 
detailed account of the sporogonium. The plants grew on the surface of 
a path, the individual thalli closely overlapping one another. The form 
of a single complete plant developed from the spore was not ascertained, 
since the branches were mostly in continuity with older underlying portions. 
The individual lobes or branch systems attained a length of 5-10 mm., and 
widened out from a narrow base to a breadth of 12 mm. or less. The 
thallus thus assumed the usual suborbicular form, and the numerous growing- 
points in the anterior margin were separated by rounded or spathulate 
middle lobes (Fig. 1). For the most part the thallus, which had no definite 
midrib, was six to eight cells thick. Each of the smaller cells of the 
limiting layer above and below contained a single large chloroplast. The 
internal cells were large and clear, and some of them contained mucilage ; 
intercellular spaces containing mucilage were absent. In the middle lobes 
the internal tissue became reduced to a single layer of mucilage cells, and 
at the extreme margin was wanting, the lobe being composed of two 
layers of cells. The apical region resembled that of N. orbicularis , and 
numerous mucilage pits, some of which were later occupied by large oval 
colonies of Nostoc, were present. The antheridia and archegonia were 
situated behind the apical regions on the same individuals. Usually a pair 
of large antheridia occupied the antheridial cavity, but sometimes three 
were found, and occasionally the antheridium was solitary. The incon- 
spicuous sunken archegonia resembled those of N. orbicularis. Fertilization 
appears to take place when the archegonia are close to the apex, and as 
a rule further growth of the thallus is slight, so that the sporogonia are 
situated close to the margin of the thallus (Figs. 1, 2). Occasionally 
sporogonia were found further back on the thallus. 
The calyptra enclosing the sporogonium was directed forwards, parallel 
to the surface of the thallus (Figs. 1, 4, 5). It measured from 1*5 to 2-5 mm. 
in length by about *75 mm. across. The side turned away from the thallus 
bore a number of longitudinal wing-like ridges, and the calyptra was 
thicker on this side than the other. The mature sporogonium usually 
projected only a short distance from the calyptra. Its length varied from 
2 mm. to 4-25 mm., but dwarf forms, like those mentioned by Leitgeb, were 
also seen, in which the total length was under 1 mm. (Fig. 3). The bulbous 
foot, the superficial cells of which grew out into processes, was separated 
from the cylindrical slightly curved capsule by a slender stalk (Fig. 4). 
The mature capsule itself was from 1*5 to 3-75 mm. long. The superficial 
cells of the wall were more or less rectangular, and their anticlinal walls 
were strongly thickened and of a brown colour. The line of dehiscence, 
was clearly marked, the margins of the two valves being formed of narrower, 
reddish-brown cells. The opening of sporogonia attached to the plant was 
