468 MR. JOHN MIERS ON A NEW GENUS OF THE BURMANNIACEA. 
to compare the active fovillæ of the pollen-grain with the spermatozoa of animals, and to 
indicate the correspondence of their main function *. 
I will not attempt to deny categorically the truth of the doctrine now universally en- 
tertained, that it is the pollen-tube alone, simply by its impact on the embryo-sae, which 
effects the fertilization of the ovule; for it must be confessed that this theory, if founded 
upon fact, is one which seems to fulfil all the conditions necessary to account for the 
phenomena of impregnation. The fact itself, if universal in its operation, is one that 
ought to be patent to every observer; but I can safely affirm that in the numberless 
instances in which I have searched for the presence of a pollen-tube in the foramen of 
the ovule, I have never yet been able to discover one. This is an objection of no weight 
whatever, as it might well arise from my obtuseness of vision, or a want of suffieient 
dexterity. As, however, I shall be able to show that such a mode of impregnation does not 
oceur in Myostoma, and as the belief in the doctrine referred to as applicable to all pha- 
nerogamous plants is now so universal, I thought it desirable to sift the evidence we have 
on record, and which I now adduce, upon which this general belief is founded. It 
appears to me that this review will induce most persons, who have not prejudged the 
question, to come to the conclusion that the very important fact alluded to has not yet 
been satisfactorily proved. 
The proofs of the facts under consideration are generally supposed to be furnished by 
Mr. Brown’s celebrated memoir “ On the Organs and Mode of Fecundation in Orchidee 
and Asclepiadee,” published in the 16th volume of the Linnean Society’s Transactions. 
I have examined that memoir with great care, but can nowhere perceive any fact ad- 
vanced to support the belief above mentioned as regards the agency of the pollen-tube; 
on the contrary, I will show, by quoting Mr. Brown’s own words, that his important 
evidence does not point to that conclusion. 
Mr. Brown, with his usual caution and profound sagacity, remarks that Amici first 
announced the discovery of the penetration of the pollen-tubes into the cavity of the 
ovarium in several plants, and believed (though he never saw it) that in every case of 
fertilization a pollen-tube comes into contact with the ovule; and Dupetit Thouars fan- 
cied he saw in Orchideæ ramifications from pollen-cords mixing with the ovules; but 
Mr. Brown states positively that his own observations had not advanced so far on that 
important point, and “that what he had to adduce concerning Asclepiadee made him 
hesitate still more from adopting these statements ” ( c. p. 707). It will be seen 
that his own details support this disbelief. He observed in Bonatea, and in general 
among the Orchidee (p.727), prior to the evolution of the pollen-tubes, a series " 
* The surprising vital energy of the fovillæ, and the rapidity of the motion of these particles, which vary a 
ably in size (from 7000 tO 55159 of an inch), though first seen by Gleichen a century ago, was scarcely noticed 
until Brown called attention to the fact, which he fully described (R. Brown, Misc. Bot. Works, i. 466). The 
circumstance again fell into oblivion after the general belief in the theory of the agency of the pollen-tube in mE 
nation ; but lately M. Faivre has once more called attention to the subject (Bull. Soc. Bot. France, vii. 772) wi 
deatritied the “mouvement Brownien” in the pollen of Gloxinia, which, he says, is of long duration, the m 
having not only a rotary motion round their axis, but a lateral sliding, and an advance of one particle beyond — 
and he also observed that a conjunction of these granules sometimes takes place : this last circumstance was also | 
by Brown in the pollen of Lolium perenne (l. c. p. 463). 
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