116 



as early as 1672, a small aperture in the outer epidermis of 

 the seed of various Leguminos<z, which, in his opinion, was 

 destined to convey air to the embryo and to facilitate the pas- 

 sage of the radicle. Subsequent observers declared this small 

 hole to be the aperture through which the ovule was impreg- 

 nated, without, however, giving any positive observations on 

 the subject. In 1806 Turpin proposed a view which also 

 ascribed to the round aperture in the epidermis of seeds the 

 function of receiving the fructifying substance, and called this 

 point of the epidermis the micropyle, a term which has been 

 generally adopted, although it must in the present state of 

 science also give way to a more rational denomination. In the 

 memoir of M. Dutrochet we now learn that Turpin has aban- 

 doned his former opinion respecting the function of the mi- 

 cropyle, and at present supposes that it is an aperture without 

 any physiological function *. 



M. Dutrochet, on the contrary, regards the micropyle as a 

 pneumatic tube which conveys to the interior of the seed the 

 air requisite for respiration, in short he has adopted Grew's 

 old notion respecting the function of the micropyle. I consi- 

 dered it to be my duty to prefix this short historical notice to the 

 subject in dispute, but it must greatly surprise every botanist 

 who is not acquainted with the subject from personal obser- 

 vations, that at the present day such a notion can be advanced 

 by a member of the celebrated Academy of Sciences of Paris, 

 after the most splendid writings have been laid before that 



* In the most recent memoir of M. Turpin (Esquisse d' Organographie, 

 &c., p. 42) we find in fact these statements confirmed ; the micropyle of M. 

 Turpin is nothing further than the aperture which an involute, and at its 

 margins cohering, leaf exhibits at its extremities, therefore it has originated 

 from imperfect cohesion. "This deficiency in cohesion may be," says M. 

 Turpin, " divided into Micropyle foliaire, M. bracteen, M. antherifere, M. 

 ovarien, M. carpellaire, and M. ovulaire" &c. The aperture of the cavity 

 of the leaves of Nepenthes is considered by him as being something similar, 

 and he would term it Macropyle, but he pays no attention to this aperture 

 being provided with a lid. From this and several similar explanations of 

 M. Turpin, we should perhaps be justified in limiting this term micropyle to 

 the point of impregnation of the ovule ; for the aperture in the ovule, through 

 which the fructifying substance passes, is sometimes formed by the envelopes 

 of the ovule, and then either by the outer, or by the inner one, sometimes by 

 the apex of the nucleus, which frequently projects in a most remarkable 

 manner, but sometimes also by the apex of the embryonal sac, which fre- 

 quently projects far outpf the nucleus or the round aperture of the envelopes, 

 and thus grows to meet the fructifying substance, the pollen tube with its 

 contents. DR. MEYEN. 



