54 Mr. A. Henfrey on the Progress of Physiological Botany: 



ovule, while he never met with it when the appendix was 

 wanting. 



After fertilization, the granular white fluid contained in the 

 embryonal vesicle becomes condensed, and appears evidently 

 contained in a new cell, which shortly after subdivides into several 

 others filled with granules ; then these become extremely multi- 

 plied, and thus form the embryo which by degrees comes to 

 occupy the whole of the cavity of the nucleus. At the same time, 

 the other portion of the embryonal vesicle, that which was in 

 contact with the pollen-tube, becomes elongated upward, dividing 

 likewise into cells, but into cells which are transparent and situ- 

 ated one above another, so as to form a large confervoid filament ; 

 this traversing in the opposite direction the course followed by 

 the pollen-tube, enlarges and passes through the orifices of the 

 tegmen and testa, and becomes prolonged even into the interior 

 of the placenta (observed in Orchis mascula). 



The pollen-tube usually disappears during this period, but 

 occasionally it may still be seen with its extremity in situ, even 

 after the cells of the embryo have been multiplied. It is not rare 

 to find it in this condition in Orchis abortiva, and the author has 

 once observed it persistent even to the period when the repro- 

 ductive body had filled the whole cavity of the nucleus. 



Orchis abortiva is better adapted for these observations than 

 0. Morio, and particularly for observing the introduction of the 

 pollen-tube into the orifice of the tegmen, since in this species 

 the state of the ovule at the epoch of fertilization is such that 

 the testa only covers the lower half of the tegmen and nucleus. 

 O. maculata appeared a less favourable subject than O. Morio, 

 but it afforded proofs that the phenomena were identical in the 

 two species. The author imagines that O. pyramidalis would 

 offer great facilities for these researches, as the ovule appeared to 

 him to be extraordinarily transparent ; he was unable to follow its 

 entire development, having only at hand a single withered specimen . 



Prof. Amici states directly that he is unable to say what is the 

 real action of the pollen-tube upon the ovule in impregnation. 

 However he considers it probable, although it cannot be demon- 

 strated, that the subtile fluid of the pollen-tube filtrates through 

 the membranes into the interior of the embryonal vesicle, and 

 that the mixture of the fluids of the male and female organs con- 

 stitutes the organizable substance. It is also possible that the 

 generative power resides in the membrane of the embryonal 

 vesicle, and that the imbibition of the liquid brought by the 

 pollen is necessary to set this power in action. Other explana- 

 tions of the phenomena might be offered, the author says, but it 

 is not his intention to give himself up to speculation, to lose 

 himself in the field of hypotheses. lie adds merely one fact, 



