10 JOURNAL OF THE [January, 



penetrates to the cavity of the germen, to enter one of the seed- 

 buds (ovules) and, finally, into the embryo-sac. The extremity 

 which has passed in, now becomes filled with cells, and these 

 develop forthwith into a perfect, though as yet simple and 

 minute plantule, the so-called embryo or germ." Schleiden fig- 

 ures the process in Viola tricolor. It is needless to say that this 

 idea has long since been proved erroneous. At the present time 

 all are agreed that the only office of the pollen-tube is to bring 

 to the incipient embryo (archegonia, corpuscula) the substance 

 of fertilization. 



Figuier remarks,*^ "This tube, as M. Brongniart has shown, 

 elongates itself by a most remarkable vegetative process, insinu- 

 ating itself into the interstices of the cellular tissue, which has 

 been designated from this cause the conducting tissue, and that 

 doubtless by which it is nourished. Occupying the centre of 

 the style, this tube traverses its whole length, entering into the 

 ovary, and is there brought in contact with the ovules, penetra- 

 ting by their micropylic perforations." He gives figures of the 

 ovules of Polygonum and Viola tricolor with the pollen-tubes at- 

 tached, and other figures showing the results of Tulasne's obser- 

 vations which proved the falsity of Schleiden's theory of the 

 origin of the embryo in the extremity of the pollen-tube. 



Le Maout and Decaisne, in " Traite General de Botanique," 

 give the following account of the process of impregnation of the 

 ovule, and illustrate it with a figure of CEiiothera longiflora. I 

 quote from Mrs. Hooker's English translation.^ ■'' "Thereupon 

 (after reaching the stigma), the pollen swells, through the action 

 of endosmose, the inner membrane ruptures the outer at one of 

 the points which touch the stigma ; the pollen-tube lengthens, 

 traverses the interstices of the stigmatic cells, and reaches the 

 conducting tissue which fills the canal of the style, and which is 

 charged, like the stigma, with a thick fluid. Still lengthening, the 

 pollen-tube finally enters the cavity of the ovary, traverses the 

 conducting tissue which lines the placentre, and at last reaches 

 the ovule, when it enters the micropyle and comes in contact 

 with the cell of the nucleus (embryonic sac), its tip resting on 

 the membrane of the sac, and partly adhering to it. Soon after 

 this contact of the pollen-tube, one, or oftener two vesicles (em- 



»» " The Vegetable World," pp. 181 et seq. 

 "Pp. 156 and 157 ; flg. 750. 



