44 
CONTRIBUTIONS TO BOTANY. 
ordinary circumstances, for the facts are still undetermined that 
can prove whieh of the two theories of the nature of vegetable 
reproduction is founded on truth ; the one maintaining that the 
pollen-grain penetrates the embryo-sac, and hence comes into 
immediate contact with the body of the nucleary vesicle, in order 
to effect its fertilization ; the other denying this assertion, and 
declaring that it does not penetrate the sac, but merely discharges 
its function of impregnation, by external impression. Similar 
theories have long been disputed among zoologists, some con- 
tending that the spermatozoon does not penetrate the ovum in 
order to effect its impregnation, as mere external impact is suf- 
ficient to accomplish this function, while others declare the 
necessity of immediate contact, and that in proof of this they 
have seen the spermatozoa within the shell of the ovum. This 
point has just been determined by hlr. Newport, in a very in- 
teresting paper read before the Linnsean Society, in which he 
proves satisfactorily that the former view is conformable to 
truth. He has ascertained the important facts, that the presence 
of active spermatozoa are absolutely necessary to impregnate the 
ovum ; that this is effected by simple impact ; he has noted the 
time necessary to complete the operation, and has observed the 
internal change that immediately takes place in the body of the 
nucleus ; and moreover he has found that the spermatozoa, after 
producing this effect by simple external impact, become inert 
and lose all power of motion. Mr. Newport has suggested that 
these circumstances, by analogy, may assist in determining the 
theories in dispute among vegetable physiologists ; and he has 
pointed to the curious fact recorded by Mr. Griffith (Linn. Trans, 
vol. XX. p. 393) of the irritability or oscillatory motion seen within 
the boyaux of the pollen-grains of Dischidia at the period of 
impregnation of the ovules, which may perhaps be in some degree 
analogous to the vivacity of spermatozoa under parallel circum- 
stances. 
Before proceeding further, I will advert to some considerations 
omitted to be made in regard to the relations of the Humiriacece 
[ante, p. 25), and which did not recur to me till after the pre- 
ceding observations on the affinities of the Olacacece were printed : 
I have there stated that the Hiimiriacea present a more manifest 
affinity with the Styracece, than with the Olacacece. The 
novelty of this view renders it necessary that I should explain 
the reasons upon which such an opinion is founded. The struc- 
ture of the ovarium of Humirium will be seen to be very similar 
to that I have described as existing in the Styracece [ante, 
p. 23), with this difference, that the junction of the partitions 
between the cells, at the axis, is almost complete, with the excep- 
tion of a small portion at the summit, and this is only distinguish- 
