144 



MORPHOLOGY OP ANGIOSPERMS 





the pollen-grain with its pollen-tube and some contents, as well 

 as the ovule with its integuments and embryo-sac; and the 

 pollen-tube had been traced from the stigma to the embryo-sac. 



Fig. 65.— A-C, Orchis Mono; D, 0. latifolia; F, O. maculata; F Canna limbata. 

 A-B, young ovules, x 150; C, end of pollen-tube enlarging, x J 00; D, later sta^re 

 with two nuclei visible in embryo, x Hii>: F, more advanced embryo, x 208; F, 

 considerably later stage, x 125.— After Schacht.' 



In 1835 Schleiden, the founder of the cell-theory, traced 

 the pollen-tube in a large number of widely separated families. 

 He claimed to have seen the tube enter the micropyle, press into 

 the embryo-sac, and then become itself the embryonal vesicle, 

 the beginning of the embryo. He thought that the contents of 

 the pollen-tube not only give rise to the embryonal vesicle, but 

 that the end of the tube, nourished by the embryo-sac, becomes 

 the future plant. 





