43 8 L ang. — Morphology of Cycadcan Sporangia . 
Fig. 6. Vertical (radial) section of a slightly older sorus, which shows two 
sporangia in median section : the sporogenous cells are shaded, x 400. 
Fig. 7. Vertical section of an older sporangium, showing the first periclinal 
division of the sporogenous cells, which are shaded, x 400. 
Fig. 8. Part of a transverse section of a sorus. The figure shows a single 
sporangium of about the same age as that in Fig. 7 : the sporogenous group still 
consists of four cells (shaded in the figure) as seen in transverse section, x 400. 
Figs. 9, 10. Vertical (radial) sections of older sporangia; the sporogenous 
masses are shaded. These figures illustrate the difference in form that exists 
between sporangia of the same age. x 400. 
Fig. 11. Transverse section of a sporangium of similar age to Fig. 9 or 10 : 
the sporogenous tissue, which is shaded, can be referred to the four cells shown in 
Fig. 8. x 400. 
Fig. 12. Vertical radial section of an older sporangium just before the tapetum 
becomes recognizable : the sporogenous cells are shaded, x 300. 
Fig. 13. Part of a similar section of a slightly older sporangium, showing the 
origin of the tapetum from the outer cells of the sporogenous group. / = tapetum, 
the cells of which are shaded ; sp = sporogenous cells ; w = inner part of sporangium- 
wall. x 400. 
Fig. 14. Spore-mother-cells, one of which is undergoing sterilization, x 550. 
Fig. 15. Vertical, nearly radial, section of a sporangium containing isolated 
pollen-grains. The tapetum is still present as a complete layer of cells around 
the cavity : the cells of the wall immediately outside it are crushed : t — tapetum. 
X 100. 
Fig. 16. Part of a vertical (tangential) section through a sporangium of the 
same age as Fig. 15, including the line of dehiscence, e = epidermal layer of 
thick-walled cells ; t — tapetum ; p = pollen-grains ; cl= line of dehiscence. x 300. 
Fig. 1 7. Side view of two mature sporangia : a, from the outer row of large 
sporangia ; b, from the central sporangia. The dots indicate the position of 
stomata, x x = position of line of dehiscence, x 6. 
Fig. 18. Ripe pollen -grain, showing the vegetative cell and the group of two 
cells, x 1000. 
