52 BOTANICAL GAZETTE [January 



the thallus, but only dorsal outgrowths. As the apical cell goes 

 on dividing, the receptacles come to stand on the back of the thallus 

 in a row along the median line, the antheridial appearing first, 

 the archegonial later. Occasionally antheridial receptacles are 

 again formed after the archegonial. Several rows of scales and 

 mucilage hairs, dorsal outgrowths also, surround both receptacles 

 (fig. 12). 



The first indication of a receptacle is a slight elevation caused 

 by a rapid division of the cells. My material has no early stages 

 of the antheridial receptacle; when mature it is without a stalk 

 and does not rise much above the surface of the thallus (fig. 12); 

 it is cordate in shape, with the notch toward the growing point 

 (fig. 1). The surface is markedly papillate, caused by the upward 

 growth of tissue about the antheridia, which agrees with Leitgeb's 

 description. The deep cavities in which the antheridia stand, 

 open to the surface by simple air pores, resembling those of the 

 thallus except that at times there is greater projection (fig. 13). 

 The archegonial receptacle appears in an early stage (fig. 14) as 

 a small, bulbous outgrowth of compact, rapidly dividing cells in 

 which are numerous chloroplasts containing starch. The cells of 

 the under part divide radially as well as tangentially, with such 

 regularity that a row of cells can be followed for some distance, 

 dividing into two rows, and these two later dividing again. In the 

 lower portion the divisions are tangential only, but the cells increase 

 both in length and in numbers. The lower part therefore forms the 

 stalk, while the upper part continues bulbous. The cells of the 

 thallus below the receptacle remain compact, while those on each 

 side form porous tissue, growing rapidly and arching up around, 

 so that the receptacle stands in a slight depression (fig. 12) until 

 after the archegonia are mature. Fertilization probably takes 

 place very easily. Later the stalk elongates and lifts the recep- 

 tacle above the surface; it may attain the length of 3 or 4 mm. 



Air cavities appear early in the developing receptacle, starting 

 about the same time as the archegonia, the origin being like that 

 of the cavities of the thallus. The split occurs first at the juncture 

 of epidermal and hypodermal cells (fig. 10), between cells of different 

 segments of the apical cell, cells derived from the same segment 



