330 Durand : Marchantia polymorpha 



first division-wall, the proximal cells constituting about one half 

 of the embryo give rise to the stalk and foot, while those of the 

 distal half become the capsule. The line of demarcation between 

 them is not always clear-cut, and generally coincides very nearly 

 with the first transverse wall ; but often it does not so coincide, and 

 certainly does not necessarily do so. 



As the young sporogonium enlarges, the superficial cells of 

 the capsular portion stain less deeply and become sharply set off 

 as an outer sterile wall of a single layer of cells enclosing the 

 deeply staining sporogenous tissue within {fig* <?7). The cells of 

 the latter at this time are irregularly isodiametric, and similar to 

 those of the stalk half. In the sporogonium figured one can detect 

 a slight bulging of the proximal tissue of the stalk to form the 

 beginning of the foot. 



A more advanced and very interesting stage is shown in figure 

 98. The whole structure has become broader ; the wall is sharply 

 differentiated from the sporogenous tissue within ; the cells of the 

 latter have increased in number, and most of them have elongated 

 somewhat in a direction parallel to the axis of the archegonium ; 

 the proximal cells of the stalk have become richer in contents, and 

 are closely applied to the tissue at the base of the archegonium, 

 into which they have begun to penetrate to form the foot. It 

 should be noted that the cells of the archegonium adjacent to the 

 foot are not crushed out nor flattened, but are plump and the con- 

 tents stain deeply. 



A 



The 



foot has penetrated more deeply into the basal cells of the arche- 

 gonium, and has expanded laterally, forming a " pileus-shaped" 

 absorbent organ, the cells of which are filled with deeply staining 

 food material in the form of elliptical bodies. The capsular portion 



Is broad, the sporogenous cells numerous and plainly elongated 

 In neither of the sporogonia shown in figures 98 and 99 is the line 

 of demarcation between the stalk and sporogenous tissue regular, 

 so that it probably does not exactly conform to the original trans- 

 verse wall of the embryo. 



In the still older sporogonium shown in figure 100, the foot 

 has become more massive and has penetrated more deeply into 

 the tissue of the base of the archegonium. The cells of the sporog- 



