THE MORPHOLOGY AND SYSTEMATIC POSITION OF PODOMITRIUM 207 
the one above it, contribute only to the haustorium, while all of the 
sporophyte itself — foot, seta and capsule — arise from the terminal 
segment, or segments. 
Fig. 6. A. Venter of archegonium containing a two-celled embryo; X about 
175. B. Two sections of an older embryo; X 175. C. Upper part of older embryo 
showing the sporogenous tissue and the elaterophore, e. D. Base of young sporo- 
phyte, showing the remains of the haustorial tissue, h. E. Upper part of young 
sporophyte, more advanced than that shown in C. 
The young sporophyte is almost cylindrical in form, and in the 
upper part, which is only slightly enlarged, the sporogenous tissue 
can be readily distinguished (fig. 6, C). The capsule wall at this stage 
is composed for the most part of two layers of cells which are decidedly 
larger in the apical region. Below the apex is a group of cells belonging 
to the sporogenous region which differ from the true sporogenous tissue 
in having less dense contents. This sterile mass of potential sporo- 
genous tissue is evidently the homologue of the elaterophore found in 
Aneura and Metzgeria, and in this respect Podomitrium differs from 
Blyttia which it otherwise closely resembles. At this stage a definite 
C- 
