214 BOTANICAL GAZETTE [SEPTEMBER 
14. JoHNson, D. S., A new type of embryo sac in Peperomia. Johns Hopkins 
Univ. Circ. 195: 19-21. pls. 5, 6. 1907. 
15. Luoyp, F. E., The comparative embryology of the Rubiaceae. Mem. Torr. 
Bot. Club 8:1-112. pls. 8-15. 1902. 
16. Overton, E., Beitrag zur Kenntniss der ooucctn: und Vereinigung der 
Geschlechiaproducts bei Lilium Martagon. Zurich. 1891. 
, Ueber die Reduktion der Chromosomen in den Kernen der Pflanzen. 
Vierteljahresch: Naturf. Gesells. Zurich 38: 169-186. 1893. 
, On the reduction of the chromosomes in the nuclei of plants. 
Annals of Botany '7:139-143. 1893. 
19. Pace, Luta, Fertilization in Cypripedium. Bor. GAZETTE 44:353-374 
pls. 24-27. 1908. 
20. PorscH, O., Versuch einer phylogenetischen Erklirung des Embryosackes 
und der Sor eslien ee der Angiospermen. 1907- 
21. ScHNIEWIND-TuIES, J., Die Reduktion der Chromosomenzahl und die ihr 
folgenden Ketathehaiigen i in den Embryosackmutterzellen der Angiospermen. 
Jena. 1901. 
22. SuirH, R. W., A contribution to the life history of the Pontederiaceae. BOT 
GAZETTE 25: 324-337. pls. 19, 20. 1898. 
23. SrepHEns, E. L., A preliminary note on the embryo sac of certain Penaeaceae- 
Annals of Romany 22:329. 1908. 
24. STRASBURGER, E., Neue Untersuchungen iiber den Befruchtungsvorgang © bei 
den Phavistoeames. Jena. 1884. 
, Ueber Kern- und Zelltheilung im Pflanzenreich. Hist. Beitr. T. Jena. 
1888 
, The periodic reduction of the number of chromosomes in the life 
heise of living organisms. Annals of Botany 8:281-316. 1894- : 
=e brat: Ms es igus. J. F. A., Notice sur le développement du s4 
Archives Neerlandaises 15:45?” 
4 o = 
456. pls. 2. 1880. + th 
. Went, F. A. F. C., The development of the ovule, embryo sac, and egg in the 
; Podostemaceae. Recueil Trav. Bot. Néerl. 5:1-16. pl. I. I ‘ 
29. WiEGAND, K. M., The development of the embryo sac in some » monocot 
ledonous plants. ‘Ber: GAZETTE 30:25-47. pls. 6, 7. 1900. 
EXPLANATION OF PLATE XV 
All figures were drawn with the aid of a camera lucida. The magnification 
in all the drawings is 670 diameters. The micropylar end is upward _ 
drawing. 
Fic. 1.—Mother cell in synapsis stage; without tapetal cell. 
Fic. 2.—Mother cell in prophase stage of first division; two cell layers 
the epidermis and the mother cell. : ple 
Fic. 3.—Early metaphase stage of the mother cell, showing thick dow 
chromosomes characteristic of first reduction division 
“pea 
oO 
betwee 
