1900] LIFE HISTORY OF SILPHIUM 131 
Fig. 55. S. integrifolium. Second division inpollen mother-cell. (Iron- 
alum-haematoxylin. 
Fig. 56. S. integrifolium. Tetrad. (sag-rek Aeles 
Fic. 57. S. integrifolium. Young pollen grain. (Saf.-gen.-violet.) 
Fig. 58. S. integrifolium. Older pollen grain, with large vacuole and 
growing spines. (Cyanin-erythrosin.) 
G. 59. S. integrifolium. Pollen grain with vegetative (v) and genera- 
tive (¢) nuclei.- (Iron-alum-haematoxylin. 
1G. 60. S. integrifolium. Generative nucleus has divided into two male 
nuclei (wz). (Saf.-gen.-violet. 
Fig. 61, a-c. S. integrifolium. Stages in development of spiral male 
cells. (Saf.-gen.-violet. 
Fic. 61,f. S. perfoliatum. Elongated male cell, showing fine nuclear 
network and delicate film of cytoplasm. (Iron-alum-haematoxylin.) 
Fig. 62. S. integrifolium. Pollen grain in detail, showing vegetative 
nucleus, two male cells, prismatic structure of onine, and the “sheath” 
derived from the tapetum. (Iron-alum-haematoxyli 
FIG. 63. S. terebinthinaceum. Pollen grain, siesbiate the last; details of 
exine and sheath not drawn. (Iron-alum-haematoxylin.) 
PLATE VIII 
Fig. 66 magnified 130 diameters ; all other figures, 1375 diameters. 
Fie. 64. S. laciniatum, Fertilization; pollen tube (/. ¢.) passing outside 
the nucellar cap; male nucleus within the oosphere. (Fuchsin-iodin-green.) 
Fic. 65. S. integrifolium. Dividing primary endosperm nucleus near tip 
of oospore ; cap (ca) still perched on end of embryo-sac. (Saf.-gen.- violet.) 
Fic. 66. S integrifolium. Diagram of sac, showing two-celled embryo 
and five spindles in endosperm ; the synergid (sy) might be mistaken for a 
pollen tube. 
Fic. 67. S. integrifolium. First division in oospore; synergid and 
nucellar cap, 
FIG. 68. S. terebinthinaceum. Two-celled embryo ; nuclei preparing for 
next division, __ 
FIG. 69. S. integrifolium. Embryo with three cells, probably by division 
of vesicular cell of fig. 68: c, in all figures, designates the cell below the 
Octants, or its product. 
FIG. 70. S. terebinthinaceum. First longitudinal wall in embryo cell, in 
radial plane. 
Fic. 71. S. integrifolium. Similar embryo, side view. 
FiG. 72. S.terebinthinaceum. Quadrant stage in embryo cell, by two longi- 
tudinal divisions. 
