or THE UNIMPREGNATED OVULUM. 445 



In 180G Mons. Turpin^ })ul)lislicd a memoir on the organ 

 l)y which the fecundating fluid is introduced into tlie vege- 

 table ovulum. The substance of this memoir is, that in all 

 Phccnogamous plants fecundation takes place through a 

 cord or fasciculus of vessels entering the outer coat of the 

 ovulum, at a point distinct from, but, at the period of impreg- 

 nation, closely approximated to the umbilicus ; and to the 

 cicatrix of this cord, which itself is soon obliterated, he 

 gives the name of Micropyle : that the ovulum has two coats 

 each havingits proper umbilicus, or, as he terms it,omphalode; 

 that these coats in general correspond in direction ; that 

 more rarely the inner membrane is, with relation to the 

 outer, inverted ; and that towards the origin of the inner 

 membrane the radicle of the embryo uniformly points. 



It is singular that a botanist, so ingenious and expe- 

 rienced as M. Turpin, should, on this subject, instead of 

 appealing in every case to the unimpregnated ovulum, have 

 apparently contented himself with an examination of the ripe 

 seed. Hence, however, he has formed an erroneous opinion of 

 the nature and origin, and in some plants of the situation, 

 of the micropyle itself, and hence also he has in all cases 

 mistaken the apex for the base of the nucleus. 



A minute examination of the early state of the ovulum 

 does not seem to have entered into the plan of the late 

 celebrated M. Richard, when in 1808 he published his 

 valuable and original Analyse du Fruit. The ovulum has, [5w 

 according to him, but one covering, which in the ripe seed 

 he calls episperm. He considers the centre of the hilum 

 as the base, and the chalaza, where it exists, as the natural 

 apex of the seed. 



M. Mirbel, in 1815, though admitting the existence of 

 the foramen or micropyle of the testa,' describes the ovulum 

 as receiving by the hilum both nourishing and fecundating 

 vessels,^ and as consisting of a uniform parenchyma, in 

 which the embryo appears at first a minute point, gradually 

 converting more or less of the surrounding tissue into its 



^ Annal. du Mus. d'HisL Nat. vii, p. 199. 



^ Elan, de Physiol. Veg. et de Bot. torn, i, p. 1-9. 



^ Id. torn, i, p. 314. 



