MR. JOHN MIERS ON A NEW GENUS OF THE BURMANNIACER. 467 
all charged with numerous ovules; these are suspended by their funicles, and grow into 
seeds, each provided with the ordinary number of integuments. It therefore seems 
extraordinary that, with all these appliances just as we see them in the most perfect 
Phanerogamia, after the fertilization of the ovules and the growth of the seeds, no in- 
dication can be detected of the presence of a cotyledonous embryo, which invariably is 
generated by the same sexual apparatus in all Exogens and Endogens. 
Many of the most celebrated physiological botanists have maintained ( and their views 
have obtained general assent) that in fecundation it is a necessary part of the function 
that the pollen-grains, on touching the stigma, should emit those capillary prolongations 
known by the name of boyaux, or pollen-tubes, which then descend along the style 
by foreing their way through its external channels, which in ordinary cases are con- 
nected through other similar passages within the ovary, communicating with the pla- 
cente; it is further maintained that, in order to fertilize an ovule, it is essential that 
one or more of these pollen-tubes should travel thus far, so as to enable it to reach the 
foramen of the ovule which it enters, thus coming into contact with the embryo-sac, 
when, by the stimulus exerted by this mere juxtaposition, it gives rise to the formation of 
a germinal vesicle within the sac, which grows into an embryo, the sac affording nutri- 
tive power to the embryo by its connexion with the chalaza. 
This ingenious theory of the agency of the pollen-tube, so willingly and so generally 
accepted, is, however, doubted by some botanists, who have brought many strong argu- 
ments to prove its fallacy. Among these, one of the most disconcerting is the impro- 
bability that a pollen-grain should possess the potency of suddenly emitting a tube the 
length of 20,000 times its own diameter (for it would sometimes require to be 6 inches 
long), and drive forward this delicate thread against the powerful resistance which mere 
friction would impede to its progress through a channel of such length and equally ex- 
treme tenuity ; it becomes, indeed, an argument of great weight that the power necessary 
to effect this would be too enormous to be supported in a fabric of such delicate texture 
—a power which no one has seen, and which no reflecting mind can believe to exist. It is, 
moreover, argued that where such pollen-tubes have been seen, or rather are supposed " 
have been seen, at the termination of the stigmatic channels, the eye has been deceive 
by appearances arising from another well-ascertained structural development of a very 
different nature, which may easily be mistaken for pollen-tubes. ; Le 
There appears much reason in these arguments, and not less so 1n um ay 
been advanced; and if they hold their ground, we must fall back again iie j # 
müquated but by no means irrational view, that it is not the pollen-tube, 5 send 
the fluid material contained in the pollen-grain, and emitted from its nui = Lu 
oe agent in the process of fertilization. No one can doubt that suc de gate 
readily be conveyed through the extremely narrow channels of the style by the TOINE 
law of capillary attraction ; by such means directly or indirectly, tbe fluid wou get ù 
i : -ne the foramen, the fertiliza- 
e D reves extremly af Aa E dicic bane ode of stimulation similar 
da Would be effected by its impact upon the ene m 
0, and as feasible as, that of the impregnation of the ovum, 
known to be universal 
i : ined, 
throughout the animal kingdom. It is only a revival of a doctrine long entertaine 
