MR. JOHN MIERS ON A NEW GENUS OF THE BURMANNIACER. 471 
spects : it never enters the embryo-sac, but deviates a little on one side during the elon- 
gation of the confervoid thread. In the progress of this growth, he observed (p. 8) the 
pistillary cords extending nearly to the base of the ovary, lying alongside the placenta, 
presenting the appearance of pollen-tubes, and seemingly continuous with those seen 
on the stigma, derived from pollen-grains. This corresponds precisely with all that 
Mr. Brown minutely describes, who affirms positively that they are not pollen-tubes, 
though greatly resembling them. Prof. Henfrey's memoir, therefore, does no more than 
eonfirm the very accurate observations of Mr. Brown, and affords no better proof of the 
conveyance of the pollen-tubes from the stigma to the mouths of the ovules, or of their 
immediate agency in the act of fecundation. 
Though the existence of pollen-tubes cannot be doubted, their utility and their true 
function may admit of another interpretation. It should be remembered that they are 
not formed of ordinary cell-structure—that is to say, of pointed consecutive cells capable 
of self-extension, which would admit the possibility of their progressive growth to any 
length desired; but, as Mr. Brown has described them, each pollen-tube is a single 
elongated cell produced by the mere expansion of the delicate pellicular inner tunie of 
the pollen-grain, and which, from the manner of its production, must be of very limited 
length; and though longer in some cases, in most instances they are rarely seen longer 
than the diameter of the pollen-grain. This extension is evidently a contrivance for 
some special purpose, the design being probably that it may be able to penetrate the 
mouths of the stigmatic channels, and serve as a funnel for pouring out and dires 
the eourse of the fluid contents of the pollen through these *' mucous-tubes ” to their 
ultimate destination. i 
The structure seen in the Burmanniacee seems to favour this view of the subject. I 
have shown, on a former occasion, that in all the genera of the tribes Burmannieæ and 
Dictyostegieæ the communication between the stigmata and placentæ 1s direct and 
perfect, and that the pollen-grains in Dictyostega emit copiously an entangled icd 
mass of delicate threads, which strongly adhere to the stigma, and show the zn 
üricles of the pollen-grains suspended from their extremities ; bob there is no evi- 
dence to demonstrate that these threads, which enter the stigmatic channels, are sé 
tinued beyond their orifices and carried to the placentz. Analogy strongly points ; 
the negative; for in Myostoma and Ophiomeris there is a want of all od means a 
Communication between the style and the placentæ, the stigmatic pue | 
the base of the style. Now, if it were essential for the fertilization of the ovules, 
Prevailing doctrine insists, that the pollen-tubes should be prolonged so as to (in “4 
ules in the bottom of the cell of the ovary, then we a a aia "r of a 
of the style into the cavity of the cell; and as the ovary PRA nn bundle 
hundred ovules, the pollen-tubes in corresponding number would form à that, as no 
Which could not escape observation. It is therefore only necessary to nu E e 
Such fascicle of threads is to be seen in Myostoma, we have it speras i 
ilizati its ovules is dis- 
Case, the theory of the application of pollen-tubes for the fertilization of its 0 
i : ined, that 
tinctly disproved. On the other hand, if we here adopt Be Fe ende in 
the fluid contents of the pollen-grains alone pass through the stig 
37 2 
