60 Mr. A. Heiifrey on the Progress of Physiological Botany : 
developed out of the middle cells of the series, and thus presents 
two appendages at a certain stage. 
Begonia cucullata offered a very favourable opportunity for the 
investigation, from the great transparency of the cells of the coats. 
Here Muller states that he is certain that the germinal vesicle is 
formed by a cytoblast in the cavity of the embryo-sac. In Bla- 
tine alsinoides the coats of the ovule are so much developed that 
it becomes necessary to make a section of the ovule to see what 
goes on in the embryo-sac. In this plant again the fertilization 
was found to occur precisely as in the preceding species — the pro- 
gress of the phsenomena is here exceedingly rapid. In Epilobium 
angustifolium the embryo was found to be developed in the same 
manner, but the author could not trace the pollen- tube to the 
embryo-sac, a section of the ovule being necessary here also. 
W. Hofmeister'!^ has published an account of a series of obser- 
vations on the impregnation of the (Enotherece, his examples being 
Godetia quadrivalvum, G. ruhicunda, (Enothera longiflora, (E. SeU 
lowii and Boisduvallia concinna. His results are in perfect ac- 
cordance with those already noticed as to the real operation of 
the pollen-tube upon the embryo-sac ; he finds that the pollen- 
tube does push it inwards a little distance in some instances 
where the embryo-sac is very delicate, in other cases it is itself 
distorted by the resistance of the embryo-sac. 
The first phaenomenon which presents itself in the embiyo-sac 
is an accumulation of the protoplasm at the micropyle end of the 
embryo-sac, and in this we soon find from two to four free cell- 
nuclei. Hound one of these nuclei (cytoblasts) a cell forms, which 
is the germinal vesicle ; a second is next produced, which some- 
times divides into two. From one of these the embryo is deve- 
loped ; and that this is the case, and that the end of the pollen- 
tube does not become the embryo, is the more certain, since at the 
time of fertilization the pollen-tube and embryo-sac are so firm 
that they may be separated with a needle under the microscope ; 
the fertilizing matter must therefore pass through three mem- 
branes, viz. those of the pollen-tube, of the embryo-sac, and of 
the germinal vesicle itself. 
In Godetia traces of the pollen-tube were found even in the 
ripe seed, and during the progress of the development of the em- 
bryo here the pollen-tube branches as it lies in the canal of the 
inner coat of the ovule, while the cellular layer around the em- 
bryo-sac has been absorbed, so that the latter with the contained 
embryo lies free in the ovule. 
• Untersuchungen des Vorgangs bei der Befructung der Ginotheren, von 
W. Hofmeister. — Botanische Zeilung, Nov. 5, 18-17. 
