2 10 
Lang . — On the Sporogonium of No to thy las. 
Fig. 7. Transverse section of a similar sporogonium. x no. 
Fig. 8. Longitudinal section of a lobe of the thallus, showing an embryo in position; the 
endothecium and amphithecium are separated in the upper tier, x 190. 
Fig. 9 a, b , c. Young embryos in median section, showing successive stages of segmentation* 
x 530- 
Fig. 10. Median section of more advanced embryo, in which all the regions of the sporogonium 
have been laid down, x 375. 
Fig. 11. Slightly older stage showing the rapid growth of the terminal group of archesporial 
cells, x 375- 
Fig. 12. Median longitudinal section of the lower portion of the sporogonium in Fig. 5. In the 
upper part the wall of the capsule can be distinguished from the sporogenous tissue, the cells of 
which are differentiated into spore-mother-cells (shaded) and elaters. Traced downwards the 
central portion of the sporogenous tissue is continuous with the endothecium, while the peripheral 
portion comes from a layer of cells which have a common origin with the wall, x 250. 
Fig. 13. Transverse section of a sporogonium at about the level aa in Fig. 12. The uniform 
sporogenous tissue (shaded) can be seen to be composed of four central groups of cells (endothecium) 
and a surrounding layer derived from the amphithecium. x 250. 
Fig. 14. Two successive sections of the sporogenous tissue at a level corresponding to b, b in 
Fig. 12, to demonstrate the absence of a sterile columella and the relation between the elaters and 
spore-mother-cells, x 250. 
Fig. 15 a, b , c, d, e. Successive transverse sections of a sporogonium, in which one of the four 
rows of cells of the endothecium is forming a sterile columella. In d and e the sporogenous cells are 
shaded, the sterile quadrant being left clear. The origin of the amphithecial archesporium can be 
followed, x 250. 
Fig. 16. Longitudinal section of the basal region of an almost mature capsule, showing a short 
sterile columella derived from the endothecium. x 190. 
