Ill 



MARCHANTIEyE 



6i 



is formed, and the young sporogonium becomes dumb-bell 

 shaped. By this time a pretty definite layer of cells (Fig, 

 2 1, F) is evident upon the outside of the capsule, but the 

 cells of the globular lower part, or foot, are nearly or quite 

 uniform. They are larger than those of the capsule, and more 

 transparent. In the latter the wall becomes later more definite, 

 and remains but one cell thick until maturity. The arrange- 

 ment of the cells of the archesporium is very irregular, and until 

 the full number of these is formed they are all much alike. 



- y 



Fig. 22. — Targionia hypophylla (L.). A, Median longitudinal section of older embrj-o enclosed in the 

 calyptra {cat), x8o; B, a portion of the upper part of the same embrj'o, X4S0; the nucleated 

 cells represent the archesporium ; C, part of the archesporium of a still later stage ; el, elaters ; 

 sp, sporogenous cells, X 480. 



Just before they separate, however, careful observation shows 

 that two well-marked sorts of cells are present, but intermingled 

 in a perfectly irregular way. A part of these cells are rjearly 

 isodiametric, the others slightly elongated, and the nuclei of the 

 former cells are larger and more definite than those of the 

 latter. At this stage the cells begin to separate by a partial 

 deliquescence of their cell walls, and when stained with 

 Bismarck-brown these mucilaginous walls colour very deeply, 

 and the cells are very distinct in sections so treated. They 

 finally separate completely, and the much -enlarged globular 



