No. II.] 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 



