10 Dr. G. Dickie on the Physiology of Fecundation in Plants. 
attached to the embryo. The ripe seed of this plant, as well as 
other Orchidea, is quite destitute of vessels * ; in Narthecium ves- 
sels do not appear until some time after fecundation. 
It is exceedingly probable that the emission of such shining 
tions, ovule-tubes as they may be called, to meet the descending 
pollen-tubes, may be of frequent occurrence. It is possible that 
some of those cases in which pollen-tubes are described as having 
been seen entering the foramen of the ovule, may have been in- 
stances of such prolongations as exist in Narthecium. 
Supposing it to be a settled pomt that contact of pollen-tubes 
with some part or other of the ovules is necessary to secure the 
full development of the embryo,—and some authors are of this 
opinion,—there seem many physical difficulties in the way of the 
pollen-tubes reaching their destination; these have reference to 
the length of the style, the nature of the tissue of which it con- 
sists, the form of the ovule, the position or direction of the ex 
ostome, the number of the ovules and other circumstances. Sure 
it is, that difficulties cannot stand before demonstration. True 
pollen-tubes have no doubt been in many instances traced into 
the tissue of the stigma and style, and in some cases to the pla- 
centa, and it may be, even to the ovule itself, but imstances of 
this last are far from numerous. In order to secure the effect of 
the pollen upon the ovule, or at all events to diminish the chance 
of this action failing, it may not be unreasonable to expect that 
some such arrangement would be provided as that, the existence of 
which in Narthecium I have been attempting to prove. Observers 
so frequently meet evident instances of design in the structure 
of organs,—it may even be said of less importance than those un- 
der discussion,—that it is extremely probable the present may be 
a case in point. 
It has been already remarked, that the number of the ovules 
presents a difficulty m the way of the contact of a pollen-tube 
with each ; and where they are very numerous and arranged in 
regular series from the base to the apex of the placenta, it is very 
evident that those occupying the latter position stand a better 
chance of being fecundated than those toward the lower part. 
The emission of tubes from the ovules to meet the descending 
pollen-tubes would evidently diminish the chance of failure. In 
such cases it would be interesting to ascertain whether all are 
usually impregnated or what proportion of them only, and whe- 
ther those taken from the upper part of a capsule contain a greater 
proportion of fecundated individuals than those from the lower 
part of the same. 
* Callitriche verna presents an instance of non-vascularity in filaments 
and anthers. 
