170 P>^of. Don's Descriptions of two neir Geneva of the 



natural to consider the placenta as forming a part only, than that it shoiikl 

 constitute the whole of what Ave regard as the pericarpium. 



The circumstance of buds being develo|)ed upon leaves is by no means so 

 rare an occnrrenee as Dr. Schleiden snp])oses ; fur not only Brt/op/ii/l/nni, 

 l>ut KahtneJioe, Rochect, Ec/ieveria, and other genera of CrassiUaceœ, are well 

 known to be readily propagated by their leaves, which give birth to buds, and 

 where care has been taken to cut them oft" above the point of insertion, so as 

 to avoid the possibility of any portion of the axis adhering to them. The seg- 

 ments of the leaves of ('(trdnrnine pratensis and amara separate from the mid- 

 rib in autumn, take root, and give birth to a young plant. In the autunm of 

 1836, while walking round the gardens of the Marquis of Ailesbury at Tot- 

 tenham Park, Wilts, I was much gratiiied by ol)serving a numl)er of plants of 

 a variety of the common Cabbage (Brassica oleraceu) having their leaves 

 covered with innumerable buds on the npper surface along the costcC and 

 veins. The petiole and lamina of such leaves in othei- respects presented the 

 ordinarv appearance. But the most convincing proof of the origin of ovula 

 from the carpellary leaves is afforded by a singular variety of the common 

 Wallrtoner {C/ieinnifluis C/iciri), first observed by Mr. Brown, in which the 

 stamina arc converted into open confluent car])els, which bear ovula at their 

 margins *. Tliesc facts go clearly to prove the correctness of the opinion which 

 derives the ovnla from the carpellary leaves; and I am disposed to think that 

 the case of the Yew {Ta.ri(s), singular as it is, will not be found to be an 

 exception to the general law. I might also notice the female inflorescence 

 of Ci/cas, which is clearly a modified frond, although I am aware that the 

 mode of evolution of the fronds in that genus might be objected to their being 

 leaves. 



The u'ood in Cri/ptomeria is compact, and the fibrous tissue is composed of 

 very slender vessels, tmited generally by their truncated ends, and furuished 



* Mr. Brown, who li;!S studied with great attention and success the various changes and de\ iations 

 which take place in the organs of pUuits, had the kindness to show me a series of beautiful drawings 

 of singularly instructive monstrosities, in some of which one half of the anther was seen to bear 

 ovula at its margin, while the other lobe remained in the ordinary condition, and contained pollen, 

 the filament being entirely unchanged, and showing clearly that no part of the axis was present. — 

 See Linn. Trans, vol. xii. p. 90., and vol. xiii. ]>. -212, wiiere these drawings are referred to by 

 Mr. Brown. 



