KIRKWOOD: POLLEN-FORMATION IN CUCURBITACEAE 241 
Explanation of plates 17-21 
PLATE 17. Micrampelis 
. Transverse section through part of young anther showing the formation of pri- 
mary de netal and primary sporogenous cells. 720 
2. Longitudinal section through RIE olde anther. The primary sporo- 
genous cells have become the spore-mother-c xX 720 
3. Transverse section through anther e still later stage. _ Spore-mother-cells 
usually in a single row in each locule of the anther. 9 20: 
4. Second division of spore-mother-cell. ‘Tapetum and anther-wall. 720. 
5. Microspore, tapetum, and anther-wall. >< 720. 
6. Later stage of same 72 
7. First division of spore nucleus. >< 562 
8. Division of spore nucleus completed. ss ~ near the wall. > 660. 
g. Mature pollen grain. Generative cell elon - Nucleus occupies most of 
the cell, es acdcicn obscure. Vegetative Rica to the right. 660 
PLATE 18 
Cyclanthera 
10, Vertical section through one side of the androecium, showing division of hypo- 
cee cell in the formation of primary tapetal and primary sporogenous cells. 
I. Slightly later stage of the same. To the right are shown initial sporogenous 
and aia cells, s and ¢ respectively. 480. 
12. Spore-mother-cells in synapsis stage. >< 420 
- Spore-mother-cells approaching first mitosis mother-cell. 480. 
14. Mitosis of mother-cell. >< 480. 
15. Microspores and anther-wall. >< 480. 
fevillea 
16. Vertical section through anther rudiment. 80. 
17. Transverse section through young anther. Spore-mother-cells shaded ; tapetum 
hot yet differentiated. <-48 
15. Later stage of same. Tapetum, T. XX 48 
19. Section through part of anther A 8 “gpore-csother- -cells in synapsis. 
sais cells strongly developed. 
© and 21. Successive stages in microspore formation, Multinucleate tapetal 
cells, x 480. 
PLATE 19. Aicrampelis 
Mitosis of pollen-mother-cells. Figures are drawn with an Abbé camera lucida. 
#8 Combination Zeiss 2 mm. inamersion mapond: and compensating ocular 1 
Magnification of figures I ts diameters. 
22, Normal resting ce 
23. Appearance of Ve ate cytoplasinic bodies 
25, 26. Contraction of bart and preparation for division. 
27- Showing origin of spindle. 
28-30, Metaphase, anaphase, and telophase of first division. 
3t. Mother-cell showing nuclei resulting from the first and second divisions. 
Section includes but three of the four nuclei. 
32. Young microspore. 
The 
