262 DR. ALLEMAO ON THE ORIGIN AND DEVELOPMENT OF 



anastomosing in a very beautiful manner : these vascular bundles or cords also, in their 

 descent, reach the base of the bulb. Now, if we take one of these bundles and examine 

 it in its whole length, viz. the bundle c, d, e, it will be seen that in c and d it is formed 

 only of trachea?, and that in e, besides tracheae, it has dotted vessels on the outer side 

 which extend upwards till they penetrate the leaves, I, and downwards they are in com- 

 munication with the root : at f is seen a crossing of tracheal bundles, which indicates 

 that the primitive bundles, instead of divaricating from each other, cross in the centre, 

 although I confess that such crossing may not be real, but apparent, and owing to error in 

 observation, notwithstanding that I have seen it more than once : g shows a portion of 

 two roots whose vascular system is formed of a certain number of bundles, disposed in a 

 parallel direction with admirable symmetry, among which are seen dotted and scalariform 

 vessels, h : no true tracheae are observable here. 



We have in this case proved the same results which are noticed among Dicotyledons : a 

 great number of microscopical observations, made upon various plants under different 

 circumstances, have confirmed these views, which I consider to be unquestionable. 



Francisco Freire Allemao. 



Rio de Janeiro, December 11, 1853. 



Notes by the Translator. 



The foregoing microscopical observations of Dr. Allemao, which seem to have been 

 carefully made, are deserving of attention, inasmuch as they offer confirmatory testimony 

 of the truth of certain physiological facts which stand upon record. I am enabled by 

 the knowledge of his antecedent researches, published in the Proceedings of the Vellozian 

 Society, to explain his object in making the above communication : he was desirous of 

 testing the validity of the theory first suggested by Du Petit Thouars, and more recently 

 modified and supported by Gaudichaud, which contends, contrary to the views of Mirbel 

 and other eminent physiological botanists, that all woody fibres of the stem proceed from 

 the nascent leaf-buds and thence descend to the radicular extremity of plants. Dr. Alle- 

 mao states (loc. cit. Exerc. Bot. p. 104) that his observations in no way tend to support 

 this theory. The facts, he observes, are best demonstrated in the stem of Cucurbita 

 Pepo, where the dotted vessels are extremely large and conspicuous : here no reticulated 

 vessels are found in the ultimate leaves, or even in the last and its nearer internodes 

 (merithalli), although they are found in the lower and older leaves : he observed spiral 

 vessels only in the stems or leaves, as low as the ninth or tenth axil from the extremity 

 of each branchlet ; from that point, as low as the fourteenth and fifteenth axil, other 

 vessels are observed in the stem only ; but below this point he found them in the stem, 

 and more especially in the leaves, proving that all reticulated and dotted vessels ascend 

 through the stem, before they find their way into the leaves, in their progress of growth 

 upwards. On the other hand, we have evidence long ago established, which may be said 

 to be the touchstone of the various theories that have been advanced on this subject ; — the 

 fact of the formation of a circular tumour in the trunk of dicotyledonary plants, above 

 the line of a ligature tightly tied around it. This intumescence is undoubtedly produced 



