1904] OPPERMAN: LIFE HISTORY OF ASTER 361 
Double fertilization was observed in A. undulatus. 
The sperm nuclei assume the structure of ordinary nuclei at 
the time of their fusion with the egg and the endosperm nucleus. 
The development of the embryo follows the type described 
for other Compositae. 
WELLESLEY COLLEGE, 
Wellesley. Mass. 
LITERATURE CITED. 
CHAMBERLAIN, C. J., The embryo sac of Aster Novae-Angliae. Bot. GAZ. 
20:205-212. pls. 75-16. 1895. 
Coker, W.C., Notes on the gametophytes and embryo of Podocarpus. Bor. 
GAZ. 33: 89-107. pls. 5-7. 1902. 
Ernst, A., Chromosomenreduction, Entwickelung des Embryosackes und 
Befruchtung bei Paris guadrifolia L. und Trillium grandifiorum Salisb. 
Flora 91: 1-46. fils. 2-6. 1902. 
FERGUSON, MARGARET C., The development of the egg and fertilization in 
Pinus Strobus. Annals of Botany 15: 435-479. Des. 237-25. 1901. 
MarrtTIN, G. W., Development of the flower and embryo sac in Aster and 
Solidago. Bor. Gaz. 17: 353-406. pis. 19-20. 1892. 
MERRELL, W. D., A contribution to the life history of Silphium. Bot. GAZ, 
29: 99-133. Als. 7-10. 1900 : 
TRETJAKow, S., Die Betheiligung der Antipoden in fallender Polyembryonie 
bei Al/ium odorum L. Ber. Deutsch. Bot. Gesell. 13: 13-17- pl. 2. 1895. 
EXPLANATION OF PLATES XIV AND XV. 
All figures were drawn with a Nachet camera lucida and are reduced one- 
fourth in reproduction. The portion of a figure nearest to the micropylar 
end of the ovule is always toward the top of the plate. The lettering of the 
figures is to be interpreted as follows: ¢.”. €g§ nucleus; 9, oosphere,; SY, 
synergids ; £.2.‘ upper polar nucleus ; 9.7." lower polar nucleus ; #2, nucleolus ; 
en, endosperm nucleus; s.1.%, $.2.2 sperm nuclei; @, antipodals ; #c, nucellus ; 
v, vacuole. 
Fic. 1. A. multifiorus. A young embryo sac with its nucleus in the 
metaphase of division. X 600. 
Fic. 2. 4, undulatus. A young embryo sac in the two-nucleate stage; 
the nuclei are in the telophase of division. X 600. 
Fic. 3. A. undulatus. A four-nucleate embryo sac just after the second 
nuclear division. x 600. 
Fic. 4. 4. Novae-Angliae. An eight-nucleate embryo ego the three 
antipodal cells have just been laid down ; the egg apparatus is being formed 
