444 OBSERVATIONS ON THE STRUCTURE 



ovula, which it enters, if I rightly understand him, by the 

 544] funiculus umbilicalis : at the same time he seems to 

 admit the existence of the aperture in the coat. 



In 1745, Needham,^ and in 1770, Gleichen,^ adopt the 

 hypothesis of jNlorland, somewhat modified, however, as they 

 consider the particles in the grains of Pollen, not the grains 

 themselves, to be the embryos, and that they enter the 

 ovula by the umbiHcal cord. 



Adanson, in 1763,^ states the Embryo to exist before 

 fecundation, and that it receives its first excitement from 

 a vapour or aura proceeding from the Pollen, conveyed to 

 it through the trachese of the style, and entering the Ovuluni 

 by the umbilical cord. 



Spallanzaiii,^ who appears to have carefully examined the 

 uninipregnated Ovula of a considerable variety of plants, 

 found it in general to be a homogeneous, spongy, or gela- 

 tinous body ; but in two Cucurbitacese to consist of a nucleus 

 surrounded by three coats. Of these coats he rightly 

 supposes the outermost to be merely the epidermis of the 

 middle membrane or testa. Of the relative direction of 

 the testa and inner coat in the two plants in question he 

 takes no notice, nor does he in any case mention an aper- 

 ture in the Ovulum. 



Gsertner, who, in the preface to his celebrated work, dis- 

 plays great erudition in every branch of his subject, can 

 hardly, however, be considered an original observer in this 

 part. He describes the uninipregnated Ovulum as a pulpy 

 homogeneous globule, whose epidermis, then scarcely dis- 

 tinguishable, separates in a more advanced stage, and be- 

 comes the testa of the seed, the inner membrane of which is 

 5153 entirely the product of fecundation.^ He asserts also that 

 the Embryo constantly appears at that point of the ovulum 

 where the ultimate branches of the umbilical vessels per- 

 forate the inner membrane ; and therefore mistakes the apex 

 for the base of the nucleus. 



* New Microscopical Discoveries, p. 60. 



^ Oljserv. Microscop. p. 45, ^^ 6J, § cxviii. 



^ Fam. (ies Plant, toni, i, p. 121. 



^ Fiuca Aiiim. e Veget. torn, iii, p. 309—332. 



'" Gcert. de Fruct. e't Sem. i, p. 57, 59, el Gl. 



