12 JOURNAL OF THE [January, 



first year, of Finns sylvcsfris at the beginning of June of the 

 second year."^'' 



The length of the pollen-tube in angiospermous plants is de- 

 pendent on the length of the style. The time required for the 

 pollen-tubes to reach the ovules after starting from the grains, is, 

 however, very different in different plants, and is in no way re- 

 lated to the stylar elongation. "In Crocus z/i?^^?/;^' the pollen-tube 

 travels the distance (lomm.) from the stigma to the micropyle in 

 from one to three days, in Antiii inaculatuni (2 to 3 mm.) in five 

 days. The short style of many Orchids is penetrated by the 

 pollen-tube only after the lapse of several weeks or months."^* 

 The same statement is made by Hofmeister. 



Dr. Asa Gray states the known facts in the process of fertili- 

 zation of the ovule, in the following language : — ^" 



" In many kinds of pollen, the grains, when immersed in 

 water, soon distend to bursting, discharging the contents. In 

 others, and in most fresh pollen, when placed in ordinarily aer- 

 ated water, at least when this is slightly thickened by syrup or 

 the like, and submitted to a congenial temperature, a projection 

 of the inner coat through the outer appears at some one point, 

 and by a kind of germination grows into a slender tube, which 

 may even attain two or three hundred times the diameter of the 

 grain ; and the richer protoplasmic contents tend to accumulate 

 at the farther and somewhat enlarging extremity of this pollen- 

 tube. * * * * Commonly the pollen remains unaltered 

 until it is placed upon the stigma. The more or less 

 viscid moisture of this incites a similar growth, and also doubt- 

 less nourishes it ; and the protruding tube at once penetrates 

 the stigma, and by gliding between its loose cells buries itself in 

 the tissue of the style, descending thence to the interior of the 

 ovary and at length to the ovules. Fertilization is accomplished 

 by the action of this pollen-tube upon the ovule, and upon a 

 special formation within it." 



M. Detmer has examined the structures which facilitate the 

 passage of the pollen-tube into the ovule, in a great many species 

 of plants."" He states that in Welwitschia (a peculiar Gymno- 



i^Detmer, " Lehrbuch der Pflanzenphyslologie," p. 354. 



"Loc. cit., p. 358. 



" " The Botanical Text Book," Part I., pp. 258-259, 1880. 



^''Jenaisclie Zeitschr. Nat'.irwiss. XIV., 530 ; and Abstract in Joiirn. Roy. Micros. 

 Soc, Series 2, Vol. I., p. 202. See also observations of M. (i. Capus, in Anu. Sci. Nat. 

 (Hot.), Vn., p. 209 ; and abstract in Jouru. Roy. Micros. Soc, 1879, p. 910. 



