FERTILIZATION. 259 
which fecundation was effected in plants of ordinary structure, 
but it agreed with the theory formed for those plants, in 
supposing that the chief agent was an invisible aura seminalis. 
It has been since shewn by Mr. Brown, and M. Brongniart 
that the mode of fecundation in Orchidee is similar to that 
which usually obtains, and which implies the necessity of 
the application some of the pollen, to a portion of the true stig- 
matic surface, the application being followed by changes of 
a peculiar nature in each particle of the pollen so applied, 
consisting in a protrusion of the inner coat of each grain, 
and its elongation, or penetration to a greater or less extent 
into the proper stigmatic or conducting tissue.* 
This, which may be called the Bauerian theory, no longer 
accords with analogy: we have the strongest ground there- 
fore for suspecting it to be inaccurate in all its details, for 
the parts to which it attributed primary agencies, would 
now appear possessed of secondary ones alone, though these 
are of high importance. It has still however some advocates, 
who think that its extreme peculiarities are not reconcili- 
able to ordinary mode of explanation, and it therefore be- 
comes worth while remarking how far this peculiar structure 
may be made fairly applicable to the new theory, which re- 
quires the application of the pollen-mass to the stigmatic 
surface. 
Insect Agency. 
` The consolidation of the minute, usually almost ætherial 
distinct grains of pollen into two or more determinate masses, 
will be allowed to destroy the effect of the usual causes of 
application, the chief of which is the motion generally caused 
* Mr. Bauer was the first person who saw the protrusion of boyaux, 
not only in this, but in families of ordinary structure. I have seen 
sketches by him made in 1799, which shew them in Orchidex and some 
other plants. He is therefore to be regarded as the author of this theory. 
That there should have been a doubt on the subject, is only an instance 
of the value of noting with the pen whatever we sketch with the 
pencil. 
