138 : DR. J. D. HOOKER ON THE GROWTH AND COMPOSITION 
— Before dismissing the subject of carpellary placentation, I would state that the other 
‘arguments in favour of free axile placentation, to which I have alluded at the beginning 
of this communication, are, the free central placenta of Primula, and the position of the 
ovule of Tagus. I am not aware of any deviation from the free central placentation 
having been observed in Primulacee except by Prof. Henslow, who kindly placed in my 
hands for examination a monstrous flower of Primula vulgaris, in which two ovaria pre- 
sented ovules developed on the confluent margins of some of the carpellary leaves, far 
removed from the base of the ovary, and wholly unconnected with the central placenta, 
which still existed, but in a reduced form, and bore ovules. | 
The other case is that of Taxus, adduced I believe originally by M. Schleiden, who 
considers the ovule as terminating the bracteate peduncle or rachis which bears it. That 
this view is not tenable appears to me to be proved by the fact that I have found two and 
even three ovules at the apparent apex of the peduncle. I further cannot but consider 
the bracteate peduncle of the female flower of Taxus* as a genuine cone, the majority of 
the bracteæ of which bear no ovarian seale and ovule. When more than two ovules are 
developed in this cone, these almost invariably wither and disappear at a very early 
period; but I have examined partially diseased cones of Taxus, in which the second ovule 
had enlarged and persisted in a scale below the terminal one. 
With such a preponderating mass of evidence in favour of carpellary placentation, 
derived from the normal condition of both simple and compound pistilla, in which the 
relation of the parts cannot be misinterpreted, and from monstrous states of ovaries whose _ 
composition is more obscure, it does seem to me unphilosophical to call for the operation — 
of a second law to explain the comparatively few exceptional examples of placentation 
that are not at once referable to the carpellary. Of these exceptional cases, Primulaceæ, 
Caryophylleæ, and their immediate allies have always been supposed to be the most 
difficult to explain away, but Caryophyllec, both in their normal state and as monsters, 
present many cases of carpellary placentation, and Professor Henslow’s Primula demands — 
a double law for one flower, if the free axile placentation be not considered a modification | 4 
of the carpellary. j D 
If it be admitted that the floral whorls are formed from leaves, even when appearances - 
a leaf in the earliest stage of its development. A contraction below the gland separates it from the lamina of the leaf, 
which is independently developed with a convolute vernation. 
While upon this subject, I may further mention, that the bilobed lamina of Dionæa is unquestionably the true — 
- lamina of the leaf of that plant ; and that it is inflexed in early vernation, as in Drosera, to which it is so closely 
allied, and to which it is further united by means of Aldrovandra. 
Of Aldrovandra I may remark, that this very rare and singular plant has been rediscovered by Dr. Thomson in the 
immediate vicinity of Galcutta. It was originally found there by Dr. Roxburgh, but unsuccessfully sought for by 
Dr. Wallich, Griffith, Voigt, and indeed every Calcutta botanist. Though unknown in any intermediate spot between 
Europe and Calcutta, I can find no difference whatsoever amongst the specimens from these widely-sundered localities. — 
* The fleshy cup of Taxus, which is usually called a disk in botanical works, but which is regarded as an arillus by 
Schleiden, is undoubtedly the outer coat (primine) of the ovule; it is developed at an early stage as an annulus in 
immediate contiguity with the second coat (secundine) : this second coat in Taxus, as in many other Conifers, becomes 
the outermost covering of the seed, or tegmen. I have ventured to allude to this here, as I am not aware that the 
' age of the integuments of the seed and ovule of Conifere has been correctly stated in any general systematic 
work. 
