No. I1.] THE BRYOPHYTES OF CONNECTICUT. I9 
thallus so that only the tip of the neck protrudes. For this 
reason no true calyptra is developed, the function of this organ 
being assumed by a tubular outgrowth of the gametophyte, 
which encloses the base of the sporophyte. 
Although the gametophyte in the present order is so 
simple, the sporophyte shows a high degree of complexity 
when compared with the preceding groups. It consists of two 
principal parts, a spherical or flattened foot, and a long and 
slender capsule, tapering somewhat toward the apex. No true 
stalk is formed, the base of the capsule passing imperceptibly 
into an undifferentiated region composed of embryonic cells. 
These continue to give rise to new cells, which gradually 
become differentiated into the permanent tissues of the capsule. 
The presence of these embryonic cells enables the sporophyte 
to grow indefinitely, a power which no other sporophytes pos- 
sess until the Pteridophytes are reached. On account of the 
basal position of the growing region, the apex of the capsule 
is the first part to mature, and all stages of development are to 
be observed in passing from the apex toward the base. The 
cross section is approximately circular, but sometimes two 
longitudinal grooves are formed, showing where the wall will 
eventually split. The latter is relatively much thicker than 
in the preceding orders, the spore cavity being distinctly 
smaller. In the higher forms the wall is bounded on the out- 
side by a distinct epidermis, with stomata, and this encloses 
several layers of green cells separated by minute air spaces. 
The wall therefore represents a photosynthetic tissue, compar- 
able to the mesophyll in the higher plants. In the lower 
forms the wall is less highly differentiated and no stomata are 
developed. The center of the capsule is occupied by a slender 
but more or.less clearly defined columella composed of sterile 
cells, and the spore cavity is in the form of a hollow cylinder 
between the columella and the capsule wall. The cavity is 
continuous over the tip of the columella at the apex of the 
capsule. It contains both spores and elaters; but the latter 
are irregularly and poorly developed in northern species, and 
do not develop local thickenings in their walls. When the 
apex of the capsule is mature, the wall splits into two valves, 
the splits gradually extending downward as the development 
