Mar., 1923 ] 
SHOWALTER — RICCARDIA PINGUIS 
155 
The more rapid growth of the dorsal portion of the apical region tends 
to push the apical cell toward the ventral side (fig. 3, PI. XVI). This 
tendency is especially noticeable in the greenhouse plants grown from the 
Florida stock (fig. 10; see also Miss Clapp’s fig. 2). 
Text Fig. 3. Photomicrographs of successive transverse sections of the apical region 
of the thallus; sections 10 p in thickness, stained with«haematoxylin. x 175. 
Development of the Archegonium 
The apical cell of an archegonial branch gives rise to relatively few 
segments, and these branches are consequently so short that it is rarely 
possible, in examining material in toto, to detect any regularity in the ar¬ 
rangement of the archegonia with reference to the axis of the branch. In 
sections of these branches there appears some evidence to confirm the 
statements of Miss Clapp for this species, and of Campbell (1905) for the 
Anacrogynae in general (not including Sphaerocarpales), that each primary 
segment of the apical cell gives rise to an archegonium. Figures 12 and 13 
represent successive vertical longitudinal sections through the short arche¬ 
gonial branch and show the apical cell (a), a three-celled archegonium, 
an archegonium with egg and ventral canal cell formed, and a tangential 
section of a mature archegonium. 
Several thousand archegonia in various stages of development were 
sectioned and stained in an attempt to obtain the history of the behavior of 
