304 BOTANY [CHAP. X 



Letter 631 before mentioned, I found the basal portion entirely destitute 

 of ovules, their place being substituted by transparent cellular 

 ramification of the placentae. As I traced the placentae 

 upwards, the ovules appeared, becoming gradually more 

 abundant towards its apex. A transverse section near the 

 apex of the ovary, however, still exhibited a more than 

 ordinary placental development i.e. [congenitally ?] con- 

 sidered each end giving off two branches, which meet each 

 other in the centre of the ovary, the ovules being irregularly 

 and sparingly disposed upon their surfaces. 



In regard to the mere question of fertilisation, then, I am 

 perfectly satisfied, but there are other points which require 

 further elucidation. Among these I may particularly refer to 

 the contracted stigmatic chamber, and the slight viscidity of 

 its disk. The latter, however, may be a consequence of un- 

 congenial conditions as you do not mention particularly its 

 examination by any author in its natural habitat. If such be 

 the case, the contracted stigmatic chamber will offer no real 

 difficulty, should the viscous exudations be only sufficient to 

 render the mouth adhesive. For, as I have already shown, 

 the pollen-tubes may be emitted in this condition, and effect 

 fecundation without being in actual contact with the stiq;matic 



fj ^j 



surface, as occurs pretty regularly in the fertilisation of the 

 Stapelias, for example. But, indeed, your own discovery of 

 the independent germinative capabilities of the pollen-grains 

 of certain Orchidaceae is sufficiently illustrative of this. 



I may also refer to the peculiar abnormal condition that 

 many at least of the ovaries present in a comparative exami- 

 nation of the placentae, and of which I beg to suggest the 

 following explanation, though it is as yet founded on limited 

 observations. In examining certain young ovaries of A. 

 Loddigesii, I found some of them filled with the transparent 

 membranous fringes of more or less distinctly cellular matter, 

 which, from your description of the ovaries of luteola, appears 

 to differ simply in the greater development in the former 

 species. Again, in others I found small mammillary bodies, 

 which appeared to be true ovules, though I could not perfectly 

 satisfy myself as to the existence of the micropyle or nucleus. 

 I unfortunately neglected to apply any chemical test. The 

 fact, however, that in certain of the examined ovaries few or 

 none of the latter bodies occurred the placenta alone being 



