CONTRIBUTIONS TO BOTANY. 
197 
is to show that the doctrine upon this important subject, as 
taught in the best elementaiy works, is founded upon a very grave 
error. I was led into this inquiry by my desire to ascertain the 
nature of the fleshy covering enveloping the hard tunic in certain 
seeds *, and which appeared to me arilloid in its nature. This was 
contested by Dr. Asa Gray, who considered these two very oppo- 
site kinds of tunics as one baccate testa, both deriving a common 
origin from the primine of the ovule f. To this view I was un- 
willing to subscribe ; and in my subsequent discussion of the 
subject, trusting fully to the orthodoxy of the common creed of 
botanists on the development of the ovule, I argued J that the 
fleshy covering in question must be an expansion or growth of 
the placentary sheath, because it enclosed the raphe : and so it 
is undoubtedly — but not in the light of an extraneous expansion, 
as I then viewed the question. This induced me to examine, by 
personal observation, the actual progress of growth of the ovule 
in certain plants which produce what have been called anatropal 
seeds ; and I soon became convinced that I had been led into an 
error of inference, solely by my faith in the universally prevalent 
creed. Having lately completed the investigation of many 
Rhamnaceous and Anacardiaceous seeds, in which several novel 
points of structure have been observed, which are difficult to 
explain, I am desirous, before the publication of these results, 
that the real nature of the development of the ovule should be 
well understood. I therefore now proceed to show that the 
doctrine upon this subject, as at present taught, is completely 
fallacious. 
It is important to observe, that the late Mr. R. Brown, to 
whom science is so greatly indebted for his grand discoveries on 
this subject, and who in simple language first explained the 
nature of the changes that take place in the development of the 
ovule §, does notdescribe the mode of action objectionably assumed 
in the writings of physiological botanists ; and it is worthy of 
remark that he never adopted the nomenclature founded upon 
the doctrine here alluded to ||. 
To Brongniart, who pui’sued these great discoveries, the highest 
merit is due for his able and patient investigation^ into the 
* Trans. Linn. Soc. xxii. 81. t Joum. Linn. Soc. ii. 106. 
J Ann. Nat. Hist. 3rd ser. i. 276. 
§ Appendix to King’s Voyage, p. 43. 
II The way in which Mr. Brown uses the term inverted is in a compara- 
tive sense : loc. cit. p. 52, where he says, “ the inner membrane is inverted 
with respect to the external umbilicus,” or, in other words, that the cha- 
laza is opposed to the hilum ; but he does not allude to any action of 
inversion of the ovular tunics. 
IT “ Memoire sur la Genriation et le Developpement de I’Embryon dans 
