118 MR. HENFREY ON THE DEVELOPMENT 
stage of the progress. The extreme delicacy of the young prothallium renders dissection 
a matter of some difficulty, and, as in the embryotomy of flowering plants, the anatomist, 
with all the skill acquired by practice, must be content to obtain decisive observations in 
but a very small proportion of his preparations. | 
The drawings which accompany this Memoir were nearly all made by means of the 
camera lucida eye-piece, so that they represent preparations actually seen; the unimport- 
ant details alone, such as the green colouring matters, &c., being given in a conventional 
manner, except in a few separate figures devoted to the special illustration of these 
points. | 
The first part of the Memoir is devoted to an account of my own observations; to this 
is added a critical examination of those of preceding authors; and, in conclusion, a few 
remarks on the general bearing of the results upon vegetable physiology. 
As some foreign vegetable anatomists have been inclined to lay great weight on the 
quality of their microscopes, in discussing the points in dispute between different observers, - 
it may be as well to state, that my investigations were made with one of Ross’s large 
microscopes, with his l-inch, }-inch, i-inch and 4-inch objectives (about seven or eight 
years old), and the drawings sketched in with the camera lucida eye-piece, after the pre- 
parations had been fully observed with various other eye-pieces. The l-inch objective 
sufficed for most purposes; the 4-inch was useful for the spermatozoids, but in regard to 
anatomical points was chiefly used on account of the short focus, which is often advan- 
tageous where the lines of cell-walls cross above one another. "The most important point, 
however, is the clearness of the preparations observed, and on these I place my depend- 
ence as to the accuracy of my statements, since there can be no doubt of my microscope 
being quite equal to those of foreign investigators. 
I. THE PROTHALLIUM. 
The specimens which I investigated were obtained from the Chelsea and Regent’s Park 
Botanic Gardens, consisting in a great measure of self-sown plants collected from the pots 
of ferns growing in the stoves. Hence I am unable to give a very definite statement as 
to the species of ferns on which I made my observations, and can only say that they were 
chiefly species of Gymnogramma, Adiantum, Pteris and Asplenium; this is of the less 
consequence, since the phenomena appeared to differ very little in the different specimens 
in which specific distinctions were certainly known to exist. 
Plants of Gymnogramma chrysophylla and of an unknown fern were obtained in the 
earliest condition, for among the tufts of young prothallia placed beneath the simple mi- 
eroscope for separation, I often found the burst capsule of the parent plant, with the 
spores germinating within and growing out from it. Examination of these showed that 
he first change which occurs in the : 
f Spores is the bursti 
protrusion of the delicate inner a: e bursting of the outer tough coat and the 
-grain: th; rane as a kind of pouch, like a pollen-tube from the 
a une da grows longer, and sooner or later becomes divided by à 
other cases the first cell = ee 1& 2); this is sometimes formed near the spore; in 
and the isis ii 1s produced into a long filament before the cross-wall is formed, 
| en partitions off a small portion at the end. The second cell becomes 
