328 SUMMARY OF CURRENT RESEARCHES RELATING TO 



months two shoots and a root had developed from the callus, which was 

 formed at the cut end of the tendril. Roots and shoots will develop 

 also on the leaves of the same plant, and on isolated portions of inter- 

 nodes. 



Reproductive. 



Gametophyte and Embryo of Torreya taxifolia.*— J. M. Coulter 

 and W. J. G. Land have studied these stages in the life-history of this 

 plant, which occurs in a narrow belt on the east side of the Apalachicola 

 River, extending from the southern boundary of Georgia for about 30 

 miles southward. It grows associated with mesophyte vegetation, such 

 as characterises the beech-maple-hemlock forms of the woods of the 

 northern States, and has a great capacity for vegetative reproduction. 



The staminate strobilus consists of a series of closely overlapping 

 sterile bracts, in four vertical rows, enveloping the tip of the axis, which 

 bears numerous stamens. The large adaxial resin cavity which occurs in 

 the stamen occupies the site of three abortive sporangia. The male 

 gametophyte has no prothallial cell, and the male cells are very unequal, 

 resembling those of Taxus. The pollen-tube is very variable in the rate 

 and direction of its advance through the nucellar cap, sometimes 

 pushing in the embryo-sac while it is in an early free-nucleate stage. 

 The ovulate strobilus consists of four enveloping bracts, and a single 

 terminal ovule with two integuments. Extensive intercalary growth 

 below the mother-cell forms the bulk of the mature ovule and seed. 

 There is no special digestive layer around the mother-cell. The solitary 

 archegonium initial appears as soon as walls are formed, is always at one 

 side of the central axis of the gametophyte, and forms a two-celled neck. 

 The nucleus of the central cell was not seen to divide, and no trace was 

 found of a ventral nucleus. In fertilisation the male cytoplasm invests 

 the fusion nucleus, and seems to remain distinct until wall-formation at 

 the four-nucleate stage of the pro-embryo. 



In the development of the pro-embryo, four free nuclei appear before 

 wall-formation, and the pro-embryo completely fills the egg, having no 

 " open cells." A pro-embryo of 12-18 cells is the winter stage. In the 

 spring the suspensor is formed by what may be called a wave of elonga- 

 tion, beginning with the uppermost tier of the pro-embryo and extending 

 gradually downward, tier after tier, until it includes the upper region of 

 the meristematic cylinder formed by the terminal cell. Small embryos 

 are formed in the second season in the suspensor region of the normal 

 embryo, but whether they arise from the prothallial or suspensor cells 

 was not determined. The rumination of the endosperm peculiar to 

 Torreya, among the Gymnosperms, arises from the extremely irregular 

 encroachment of the endosperm upon the perisperm. 



Parthenogenesis in Wikstrcemia indica.f— Hans Winkler describes 

 the occurrence of parthenogenesis in this member of the Thymelreaceae. 

 The pollen is apparently incapable of germinating. In absence of 



• Bot. Gazette, xxxix. (1905) pp. 161-78 (4 pis.), 

 t Ber. Deutsch. Bot. Gesell., xxii. (1905) pp. 573-80. 



