unimpregnated Ovulum in Phenogamous Plants. 359 
thesis, state the general existence of an aperture in the unim- 
pregnated vegetable Ovulum. It is not, however, probable 
that these authors had really seen this aperture in the early 
state of the Ovulum in any case, but rather that they had 
merely advanced from the observation of Grew, and the con- 
jecture founded on it by Morland, whose hypothesis they adopt 
without acknowledgment, to the unqualified assertion of its 
existence, in all cases. For it is to be remarked, that they take 
no notice of what had previously been observed or asserted on 
the more important parts of their subject, while several pas- 
sages are evidently copied, and the whole account of the ori- 
ginal state and developement of the Ovulum is literally trans- 
lated from Camerarius’s Essay. Nor does the younger Geof- 
froy mention the earlier publication of his brother, from which 
his own memoir is in great part manifestly derived. 
In 1718, Vaillant*, who rejects the vermicular hypothesis 
of generation, supposes the influence of the Pollen to consist 
in an aura, conveyed by the trachez of the style to the ovula, 
which it enters, if I rightly understand him, by the 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 Morland, 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 umbilical cord. 
Adanson, in 1763§, states the Embryo to exist before fe- 
cundation, and that it receives its first excitement from a va- 
pour or aura proceeding from the Pollen, conveyed to it 
through the trachez of the style, and entering the Ovulum by 
the umbilical cord. 
Spallanzani ||, who appears to have carefully examined the 
unimpregnated Ovula of a considerable variety of plants, found 
it in general to be a homogeneous, spongy, or gelatinous body; 
but in two Cucurbitacez 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 aperture in the Ovulum. 
Geertner, who, in the preface to his celebrated work, dis- 
* Discours sur la Structure des Fleurs, p. 20. 
t New Microscopical Discoveries, p- 60. 
f Observ. Microscop. p. 45 et 61. § exviii. 
Fam, des Plant, tom. i. p. 12). 
|| Fisica Anim. e Veget. tom. iii. p. 309--332. 
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