264 DR. ALLEMAO ON THE ORIGIN AND DEVELOPMENT OF 



facts, although in the preceding communication his observations relate only to the deve- 

 lopment of the primary bud of an individual plant, that is to say, of the growing embryo 

 of a seed. He observes (loc. cit. p. 105) that Mirbel in one of his latest essays on this 

 subject (Acad. Sc. Paris, June 1843), in opposing the views of Gaudichaud, demonstrates 

 the fact that the circulating vessels ascend from the point of their origin in the stem, and 

 thence extend to the leaves, but that he does not here distinguish the difference between 

 tracheal and dotted vessels ; while, on the other hand, Gaudichaud comprehends in his 

 descending system the same vessels, both vascular and fibrous : his own observations, 

 however, conform only with the theory of Gaudichaud inasfar as regards the propagation 

 downwards of tracheal vessels, and with the latest views of Mirbel relative to the propa- 

 gation upwards of dotted or fibrous vessels ; and they are opposed to both, in respect 

 to the evolution of each fibre upwards and downwards in opposite directions*. There 

 appears to me here a misprint, or complete misapprehension of the views of Gaudichaud, 

 who clearly traces the source of each bud, not from the point of external growth, as Dr. 

 Allemao seems to infer, but, as I have above remarked, from the seat of its origin around 

 the medullary sheath, at the " nceud vital," or point of departure of each independent 

 ascending and descending system of vascular fibre. The origin of numerous distinct bud- 

 formations around the medullary sheath, and the extension of ascending spiral vessels 

 and of corresponding descending dotted vessels from each of these separately, are main- 

 tained throughout by Gaudichaud in his ' Recherches Generales ' as an essential part of his 

 theory ; and these are minutely demonstrated in pi. 7. fig. 41, 42, 44, pi. 8. fig. 4, 5, 6, &c, 

 in dicotyledonous plants, and in pi. 9. fig. 1, 2, 3, 4, and pi. 10, in monocotyledonous plants. 

 In support of his theory he also gives numerous other illustrations, even forcibly quoting 

 the same circumstances of the intumescence of a stem produced by a ligature, and the 

 germination of an apparently budless stem, both which facts Dr. Allemao considers to 

 strengthen his own views in opposition to those of Gaudichaud. 



A precisely analogous development to that delineated in the preceding memoir was 

 pointed out by Mirbel in 1809, showing the origin and formation of similar vessels in the 

 germinating seeds of Nelumbo (Ann. Mus. xiii. 471. pi. 34. fig. 19), where they are depicted 

 as originating from the neck of the plumule, and branching thence into the nervures of the 

 cotyledonary leaves, while others tend downwards into the growing radicle : these several 

 vessels were first observed by Bonnet, and described by him as " mammary vessels," as 

 far back as 1754. Mirbel described all these ascending vessels to be of spiral structure, 

 and the others tending to and through the roots, to be strangulated or dotted vessels, 

 which, though incapable of being unrolled, he considered to be only modifications of the 

 spiral form, an opinion which he afterwards somewhat modified. Long prior to this (in 

 1802), Mirbel read a memoir to the Institute, expounding these facts ; and we find a very 

 concise account by Desfontaines, of these able researches, in the 5th volume of the ' Annales 

 du Museum', p. 80, with two elaborate plates, showing the ascending system of spiral 



* His words are, " conforma se com a theoria de Seiior Gaudichaud quanto a propagacao de alto a baixo, sdmente 

 para as tracheas ; e com as obserracoes ultimas de Mirbel quanto a propagacao de baixo para cima, mas unicamente 

 para os vasos pontuados e lenhosos ; e emfim differe de todas quanto a evolucao de cada fibra em sentidos oppostos 

 para cima e para baixo." 



