466 BOTANICAL GAZETTE [December 



A cytological study of fertilization in conifers has been made for 

 a number of species: Chamberlain, Pinus Laricio (3) ; Blackman, 

 Pinus silvestris (2); Miss Ferguson, Pinus (6); Murrill, Tsuga 

 canadensis (20) ; Noren, Juniperus (22) ; and Nichols, Juniperus 

 (21). "After the male pronucleus is within the oosphere nucleus 

 the chromatin of the two pronuclei appears as two distinct masses 

 in the spirem stage" (3). "Es scheint als wiirde jede der beiden 

 Chromatingruppen zuerst ihre eigen Kernspandel ausbilden, die 

 sich dann zu einzigen vereinigen" (22). On the fibers "the long 

 bent and twisted chromosomes appear" in Tsuga (20). Miss 

 Ferguson (6) states: "When the chromosomes are being oriented 

 at the nuclear plate, the maternal and paternal elements can no 

 longer be distinguished." The number of chromosomes at this 

 stage was found to be 1%. No count is recorded during the phase 

 of pairing (or splitting, as it has generally been regarded). Miss 

 Ferguson's figures confirm what has been described for Abies. 

 Her figs. 236 and 237 may be compared with figs. 29-33; ^ er 

 fig. 238 with figs. 34-39; and her fig. 241 with fig. 51. As illus- 

 trated by diagram B, a number of stages in the process of fertiliza- 

 tion have not been described heretofore. It is not surprising that, 

 without these stages and not having the chromosome count through- 

 out, the pairing should be interpreted as a longitudinal split, and 

 that evidence of segmentation should not be found. Because of 

 the complete series found in Abies and the extreme size of the 

 chromosomes, it has been possible to discover the facts which center 

 about the pairing, followed by the transverse segmentation. 



Stages in fertilization. — A study of the union of egg and sperm 

 in plants and animals makes it evident that there are several phases 

 in the process of fertilization. The primary phase is illustrated by 

 Uredineae. Here the fusion is evidently incomplete during the 

 binucleate stages. "In the young aecidium the nuclei become 

 paired and divide together in very close association. The teleuto- 

 spores in the young state are binucleate, but when mature become 

 uninucleate by the fusing of the two paired nuclei" (1). It is only 

 after many separate but simultaneous divisions of the pairing 

 nuclei that this second phase of the process is accomplished. 

 Harper (8) believes that bivalent chromosomes are formed in 



