No. 11.] THE BRYOPHYTES OF CONNECTICUT. 21 
this fact is sometimes difficult to demonstrate. They are desti- 
tute of midribs, but show a remarkable differentiation into two 
kinds of cells: — green cells, which remain alive for a long 
time; and colorless cells, which soon lose their living contents 
and become empty. In the leaves of the spreading branches 
the green cells are united in such a way that they form a 
loose network, each mesh of which is filled with a single 
large colorless cell. The latter is characterized by a thin wall, 
usually with band-like thickenings on the inside which keep 
it from collapsing, and by holes or pores which place its 
cavity in direct communication with the outside. The stems 
and branches are usually covered over on the outside by a 
cortex composed of similar colorless cells; within this is a 
distinct zone of sclerenchyma enclosing a central pith. The 
tufted habit of the peat mosses, their upright stems covered 
with pendent branches, and their porous hyaline cells, account 
for the ease with which they suck up and retain water. The 
process is largely due to capillarity. 
The archegonia are borne at the tips of branches, and 
limit their growth just as in the Jungermanniacee. The 
sporophyte consists of a spherical capsule and a broad foot 
‘with a deep constriction between them. No true stalk is 
developed. The calyptra persists until the spores are mature, 
and is then irregularly ruptured by the dehiscence of the 
capsule. The latter while still immature contains a large 
columella in the form of a hemisphere. This is covered over, 
at the apex by the small spore cavity in much the same way 
as in the Anthocerotales, but the cavity contains spores only. 
The wall of the capsule is several cells thick, the outer layer 
forming a distinct epidermis. Some of the inner cells contain 
chloroplasts, but there are no intercellular spaces among them, 
and the epidermis develops no effective stomata, so that the 
wall can hardly serve as a very useful photosynthetic tissue. 
When the spores are mature, the upper part of the archegonial 
branch elongates rapidly, thus simulating a stalk, and the 
capsule opens by means of a circular split in the wall, which 
cuts off a cap-like lid. As the drying of the capsule proceeds, 
the pressure in the interior increases, until a sudden liberation 
takes place which shoots out the spores together with the 
