408 M. Treviranus on the Formation of Aerial Tubers 



LIX. — On the Formation of Aerial Tubers in Sedum amplcxi- 

 caule, DeC, By L. C. Treviranus*. 



If we assume, what can scarcely be denied, that individuals 

 exist even in the vegetable kingdom, it may be asserted that each 

 of them flowers only once. When a plant appears to do this 

 more frequently, it is accurately speaking no longer the same in- 

 dividual, but a different one, which has applied itself to or en- 

 grafted itself upon the first, or by whatever other name the con- 

 nexion which has become established between the two may be 

 designated. It is very distinctly evident that the flowering plant 

 is a new one when the old one dies off after flowering, but pre- 

 vious to this forms the basis of a new one in the form of a bud, 

 that is, a crude deposit of organic matter which remains connected 

 with the mother-plant for a period, at the same time putting forth 

 separate organs of nutrition, with the aid of which it becomes a 

 distinct independent individual, which flowers and propagates as 

 the parent one. Of several families of plants in which this circle 

 of propagation and flowering is perceptible in a striking manner 

 is that of the house-leeks {Crassulacece, DeCand.). In those 

 species of Sempervivum which constitute in Koch the subgenus 

 Jovisbarba, we often observe buds shoot out on thread-like pe- 

 tioles frequently an inch in length from the angles of the leaves 

 converging to form the rosette. At first globular, and only of 

 the size of a grain of millet, they soon become larger, and separate, 

 when they have attained the size of a cherry-stone or of a hazel- 

 nut, from the mother-plant, themselves sending down root-fibres, 

 with the aid of which they absorb nutriment and become deve- 

 loped. If a section of such a body be made, it is seen to consist of 

 a ground-work of compact cellular tissue, from which numerous 

 fleshy leaves take their origin. As soon as the mother-plant has 

 acquired the requisite size and development, it flowers and dies ; 

 the same fate likewise attends the newly-formed plant. 



In those species of Sedum which are herbaceous and perennial, 

 such as >S^. rejlexum, sexangulare, album, &c., some short branches 

 densely clothed with leaves shoot out of the main body of the 

 plant during and after the flowering period; they continue in 

 organic connexion with it by means of cellular tissue and ves- 

 sels until their turn comes to extend and to flower. But this 

 formation of new shoots takes place in a more remarkable manner 

 in Sedum amplexicaule^ DeC, a species occurring in the south of 

 France, in Lower Italy, in Spain and in Greece, which bears our 

 winters very well if they are not too severe, even in the open 

 ground. It was named Sedum rostratum by Tenore, but ranged 



* From the Botanische Zeitung for April 18th, 1845. 



