2G2 J)r. Dickie un the Ovule 0 / Euphrasia officinalis. 
and continuous with its neck, is merely a process of that part. 
In Euphrasia, however, the embryo-sac does not appear exter- 
nally, as in the advanced stages of that of Veronica. 
The tube already described as traversing the bulb and neek of 
the sac, and passing some way into the interior of the body of the 
same organ, is certainly not the least remarkable part of the ar- 
rangement. The principal argument against its origin from the 
pollen has been already alluded to, viz. its closed papilliform end 
projecting from the fissure in the extremity of the bulb. It is 
certainly very difficult to pronounce a decision respecting the 
nature of the extremity of a transparent membranous tube less 
than a three-thousandth of an inch in diameter. I have come to 
the conclusion mentioned, after repeated careful examination 
under various powers of a microscope (by Brunner of Paris) va- 
rying from 250 to upwards of 600 diameters. Figure 1 repre- 
sents a preparation in my possession, in which two tubes are 
lying beside each other ; one of them is evidently broken across, 
the other is closed at the end ; the latter may be traced to the 
exostome of an ovule, part of which only is represented. The 
ruptured tube belonged to another ovule which is not represented 
in the figure. But for the fact just mentioned, I should feel con- 
strained at once to admit, that appearances are much in favour 
of Schleiden’s opinion, excepting that part which has reference 
to the introflexion of the ernbryo-sac. 
It will now be evident, therefore, that in Euphrasia, the ovule 
tubes are not prolongations of the apex of the nucleus, but pro- 
ceed from the interior of the embryo-sac. As already mentioned, 
I am not at present prepared to state positively the relation be- 
tween the tube and the embryo. 
The majority of observers seem to agree respecting the pre- 
sence of pollen-tubes in the tissue of the stigma and style ; and 
they have been traced into the interior of the ovarium. That 
part of the subject which has reference to the presence of such 
tubes connected with the ovule, and their nature, has given rise to 
much difference of opinion. 
Mirbel long ago pointed out the existence of tubular prolon- 
gations proceeding from some part of the ovule. Those observed 
by Mr. Brown in the Orchidece were supposed to have their exist- 
ence determined by the action of the pollen, but not to be directly 
derived from it. Schleiden spoke emphatically respecting the 
pollen-tubes reaching the embryo-sac, and the same was admitted 
by Meyen, though they differed respecting the subsequent rela- 
tions of the two. Griffith demonstrated the presence of both 
pollen- and ovule-tubes. Ilartig admitted the existence of three 
kinds in connexion with the ovules in different plants : first, true 
pollen-tubes, as in the Conifera ; second, prolongations of the 
