LEAF IN THE VASCULAR CRYPTOGAMS AND GYMNOSPERMS. 
613 
PLATE 38. 
Fig. 13. Cells at the apex of the leaf of A. evectct, the apical cells marked ( x , x). 
X 175. The arrows show approximately the median plane of the leaf. 
Fig. 14. Another example of the above : the arrangement of the cells is less regular. 
Fig. 15. Apex of the leaf of A. evecta, which has begun to form three pinnae. X 10. 
Fig. 16. Apical part of a leaf of A. evecta , which has formed 9 pinnae. The lower of 
these (2 and 3) have already begun to form pinnules. X 5. 
Fig. 17. Leaf of A. evecta with six pinnae. The phyllopodium ends abruptly 
( ap .). X 4. 
Fig. 18. Transverse section of a pinna of A. evecta showing wings ( tv, w). X20. 
Fig. 19. One of these wings under higher power. X 175. 
Cycas Seemanni. 
Fig. 20. Endosperm with embryo natural size. 
Fig. 21. Transverse section of cotyledons near the base, showing in one case a median 
bundle, in the other no single median bundle. X 10. 
Fig. 22. Longitudinal median section of the apex of a young seedling. X 20. 
Fig. 23. Similar section of am older plaint. X20. 
Fig. 24. Young leaf, ventral aspect, showing wings continuous from base to apex. 
X 20. 
Fig. 25. Horizontal section of the apex of a plant 12 months old. X 20. 
Fig. 26. Leaf of a young plant, showing the wings (tv) continuous upwards : note 
especially that the p inn ae are not in regular succession in respect of size. 
X 20. 
Fig. 27. Leaf showing the pinnae at the middle of the two series most advanced. 
X 20. 
PLATE 39. 
Fig. 28. Similar leaf showing a decided decrease in size of the pinnae in a basipetal 
direction : there was in this case no decided proof of the absence ot an 
acropetal order of development. X 20. 
Fig. 29. Transverse sections (a) of a scale-leaf, ( b) of a foliage-leaf. Scl. =sclerenchyma. 
X10. 
Cycas Jenkinsicina. 
Fig. 30. Leaf in which the formation of pinnae has begun, and showing those about 
the middle of the two series as most advanced. X 20. 
Fig. 31. a and b, the lower ends of the series of pinnae on two leaves of different ages. 
X 20. In both cases it is seen that an increase in their distance apart, 
which is due to greater elongation of the phyllopodium, is coincident with 
an arrest of development of the individual pinnae. 
