Mr. J. Cleland on Vegetable Placentation. 337 



cords in five series shows the same thing. But this is not con- 

 sistent with the axile theory. If ovules arc ever equivalent to buds 

 emanating directly from the axis, they must in every such case 

 be more or less under the law of evolution followed by the leaves, 

 and however their arrangement may seem from circumstances to 

 depart from that law, they cannot observe a system of distribu- 

 tion essentially different. We find a whorled arrangement fol- 

 lowed by every other homologue of the leaf, and should expect it 

 here too. But in the case before us, the ovules are given off 

 in vertical double rows. The objection may be started, that 

 this appearance may result from the piling of whorls one on 

 another without alternation, just as the stamen is in front of the 

 petal in the Barberry and the Buckthorn, or rows of petals 

 are piled in front of one another in abnormal specimens of the 

 Camellia. But if this explanation be adopted, we have still to 

 account for the rows being double, and for each row being con- 

 nected by vascular tissue with the one on the other side of the 

 adjoining interspace, while to its fellow it is only joined by inter- 

 stitial cellular tissue. 



On the other hand, if we adopt the ordinary marginal theory, 

 we have staring us in the face the old objection, that there is no 

 trace of any connexion ever existing between the placenta and 

 wall of the ovary ; but on the contrary, between the double 

 rows of cords where the carpels are supposed to have turned 

 inwards, we have a smooth pad of cellular substance. IMoreover 

 we should expect the rays of the central star to be pointed to the 

 interspaces instead of being in the position w^e find them in ; for 

 by this theory each pair of rows is formed from the margins of 

 one carpel and has nothing to do with the neighbouring pairs, 

 and we should therefore expect to find a (fig. 1) connected by 

 vascular tissue, not with b, but with c. 



What I wish to suggest as a better explanation than either of 

 the above is, that this placenta is formed of a second whorl of 

 carpels, distinct from and alternating with the outer carpels, and 

 bearing the ovules on their everted margins. This view accounts 

 for the arrangement of the vascular tissue. The double rows of 

 cords are considered according to it as formed from the margins 

 of two adjoining carpels, and the true fellow of each of the com- 

 ponent rows is the one at the other side of the neighbouring 

 interspace, and the bundles of fibres represent the midribs of the 

 leaves. This view" was first suggested and seems to be very con- 

 siderably supported by the monstrosity which I have figured, in 

 which two members of the inner whorl had assumed the folia- 

 ceous form (fig. 2). One of them was much contorted on account 

 of its excessive development in a confined space, but the other 

 retained its place in the whorl with its edges everted. 



Ann. i^ Mag. N. Hist. Ser.2. Vol.xv. 22 



