Sperm- Cells in Asclepias Cornuti , Decaisne, 147 
EXPLANATION OF FIGURES IN PLATE VII. 
Illustrating Mr. Gager’s paper on the Pollinium of Asclepias. 
All the figures are drawn with the aid of a camera lucida, at 140 mm. projection. 
Tube length 160 mm. Nos. 1 and 34 with Zeiss 8 ocular, and Bausch and Lomb 
2-3 objective. Nos.. 2, 3, 4, 5, 9, 17, 18, 20, 21, 22-25, 35 > 37 > with Zeiss 4 
ocular, and 2 mm. horn. imm. Nos. 3#, 8, 17^, 21 a, with Zeiss 18 ocular, and 
2 mm. horn. imm. No. 6 with Zeiss 4 ocular, and Bausch and Lomb 2-3 objec- 
tive. No. 7 with Zeiss 12 ocular, and Bausch and Lomb 2-3 objective. Nos. 10- 
16, 19, 26-32 with Zeiss 12 ocular, and 2 mm. hom. imm. Nos. 33, 36 with 
Zeiss 8 ocular, and 2 mm. hom. imm. 
Fig. 1. Cross section of bud about 1 mm. in diameter, showing the five young 
anthers and the young primary pollinium-cells radially arranged in the developing 
microsporangia, x 85. 
Fig. 2. Cross section of portion of anther much younger than Fig. 1. Develop- 
ing archesporium. x 450. 
Fig. 3. Cross section of portion of anther older than in Fig. 2. Division 
of archesporium to cut off tapetal cell, x 450. 
Fig. 3 a. Detail of division figure in Fig. 3. Fifteen chromosomes on equator of 
spindle, x 1525. 
Fig. 4. Cross section of end of anther. Division complete, cutting off tapetal 
cell, x 450. 
Fig. 5. Cross section of end of anther. Young primary pollinium-cell with 
characteristic large nucleoli. Tapetal layer developing peripherally from the 
sister-cells of the primary pollinium-cells, axially from the parenchymatous 
cells, x 450. 
Fig. 6. Cross section of nearly mature anther. Primary pollinium-cells in first 
division, x 45. 
Fig. 7. Cross section of microsporangium. Tapetal layer well differentiated. 
Primary pollinium-cells in first division, x 1 20. 
Fig. 8. Tissue cell showing twenty-four chromosomes, the full complement for 
A sclepias cornuti. x 1525. 
Fig. 9. Young primary pollinium-cells, showing vacuoles in cytoplasm and 
in nucleolus, wart-like bodies, and first appearance of the small granules in the 
cytoplasm staining like chromatin, x 450. 
Fig. 10. Mature primary pollinium-cell. Fibrous character of the cytoplasm, 
and the small granules staining like chromatin. Nucleolus vacuolated and having 
a distinct membrane. Chromatin distributed on the threads of the nuclear 
reticulum, x 1225. 
Fig. 11. Synapsis preceding the first division of the primary pollinium-cell. 
X 1225. 
Fig. 12. Nucleus of the primary pollinium-cell soon after synapsis. Nucleolus 
vacuolated and having one wart-shaped body, x 1225. 
Figs. 13, 14. Nucleoli of primary pollinium-cells showing stages that suggest 
fragmentation and a possible connexion between fragmentation and the wart-like 
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