310 Remarks on the Impregnation of Plants. 
the pollen is supposed to be deposited in, and nourished by the ovule: 
according to another, the germ is thought either to pre-exist in, or 
to be originally formed by the ovule itself, and that it is merely exci- 
ted into action by an influence derived from the pollen: and according 
to a third, the embryo is conceived to result from the union of a germ 
furnished by the pollen with another produced by the ovule.* It is 
hardly probable that we shall ever possess the means of absolutely 
proving the correctness or demonstrating the fallacy of either of these 
hypotheses ; but it may be remarked that the first mentioned view, 
which was advanced at an early period, is the most difficult to be 
reconciled either with the phenomena of hybridity or with the man- 
ifest analogy that exists between seeds and buds; and yet recent 
discoveries have again rendered it the more probable hypothesis. 
Soon after the discovery of the office of the pollen, several at- 
tempts were made to explain the manner in which this substance 
acts upon the stigma. Some of the earlier writers, such as Geoffroi 
and Malpighi, seem to take it for granted that the entire grains of 
pollen which fall upon the stigma pass down the style quite into the 
ovary ; and Moreland} suggested that the grains even penetrate the 
ovules and become the embryo. The latter author, who was, | be- 
lieve, the first to extend the hypothesis of Leeuwenhoek to the veg- 
etable kingdom, inquires “ whether it be not more proper to suppose 
that the seeds which come up in their proper involucra, are at first 
like unimpregnated ova of animals; that this farina (pollen) is a 
congeries of seminal plants, one of which must be conveyed into 
every ovum before it can become prolific ; that the stylus in Mr. 
Ray’s language, the upper part of the pistillum in Mr. Tournefort’s, 
is a tube destined to convey these seminal plants into their nest in 
the ova; that there is so vast a provision made because of the odds 
there are whether one of so many shall ever find its way into and 
through so narrow a conveyance.” He then proceeds to r 
several circumstances ; which are, in his opinion, confirmatory of 
this view; especially shee eeepeentty tubular style of the Crown Im- 
* The latter hypothesis i is ee by Ad. Brongniart with much confidence in 
his memoir above cited.—* ee es ng +... Un 0 u quelques-uns des g ranul 
spermatiques s’unissent probab!} ovule pour 
donner naissance au pi globule, premier rudiment informe dé. emibepo," &e. 
Ad, Brongniart i 
Some 
bs isin on the Parts and die Use of the flower in Plants; by 
Samvet Morevanp.—Philosophical Transactions, Vol. 23, (1703.) 
