PHANEROGAMIA : BUD ORGANS. 



295 



as occur in Bletia into the true tuber, through Monachanihus, Catasetum, 

 Dendrobium, &c., into the usual structure of stems. In an exactly similar 

 manner to that in Orchis is formed the pseudo-tuber of Aponogeton 

 distachyon. The embryonary bud is attached laterally and free upon the 

 thick, fleshy cotyledon ; the radicula is developed quite regularly at first, 

 in germination ; but the portion of the embryonary bud between the 

 cotyledonary leaf and the following soon swells up into a fleshy body on 

 the free side, and then the full-grown, round pseudo-tuber becomes sepa- 

 rated from the cotyledon, while adventitious roots have been gradually 

 developed between the pseudo-tuber and the lowest leaf of the young 

 plant.* I do not know whether new pseudo-tubers can develope in 

 Aponogeton as axillary buds of the plant. 



Lastly, in reference to the Dahlias, my investigations are still very 

 imperfect. The matter appears to me to stand thus : Two adventitious 

 roots are formed on the base of the cotyledon soon after germination. In 

 later conditions I found the young pseudo-tuber (no trace of adventitious 

 roots) under the cotyledon, but two of them pretty low down upon the 

 pseudo-tuber : I think these must have been developed between the 

 former adventitious roots and the cotyledon. I have given at length, in 

 my already often -quoted treatise on the Cactece, an account of the pro- 

 cess of multiplication of cells in the young tubers, contemporaneously with 

 the origination of oil passages. It consists in constant formation of cells 



* What Flanchon (Ann. des Sc. Nat. 1844, Botanique, p. 107, et seq. ) has published 

 on this is altogether incorrect, and, like a good deal else in the same essay, a result of 

 very superficial observation. 



179 A, Bollophyllum bulbiferum, natural size : a a, tubercular internode, the terminal 

 bud of which becomes the inflorescence; 6, leaf; c, dry, old sheathing leaves; an 

 adventitious root is breaking forth through the lowest ; </, older and non-tubercular in- 

 ternode. B, Epidendrum coc/tleatum, two- thirds of the natural size : a, b, <?, d, as before ; 

 c, the flower-stalk, cut off. 



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