364 Linnean Society. [Jan. 16, 



forming a crown around the vital point which Dr. AUemao regards 

 as the limit between stem and leaves. These tracheae are very 

 slender, vermicular or fusiform, with a curvature in the middle, the 

 convexities of which look towards the centre ; extending upwards 

 they penetrate the leaves in great number running parallel to each 

 other, and passing downwards they cross and become external to 

 the interior bundles taking a fiexuose direction. In the succeeding 

 leaves there are no simple trachese, but numerous tracheae form 

 bundles running parallel to each other as far as the extremities of 

 the leaves, and giving off lateral and transverse branches which 

 anastomose in a very beautiful manner. These vascular bundles 

 also descend as far as the base of the bulb. Above they are formed 

 entirely of tracheae ; lower down the tracheae are accompanied on 

 the outer side by dotted vessels, which extend upwards to penetrate 

 the leaves and downwards to communicate with the root. In the 

 roots the vascular system is composed of a certain number of bundles, 

 parallelly disposed with admirable symmetry, among which are seen 

 dotted and scalariform vessels, but no true tracheae, A great number 

 of microscopical observations made on various plants under different 

 circumstances have confirmed these views, which Dr. AUemao con- 

 siders unquestionable. 



The paper was accompanied by a series of notes by Mr. Miers, 

 in which, from his knowledge of his antecedent researches, published 

 in the Proceedings of the Vellozian Society, he states it to have 

 been the object of Dr. AUemao to test the validity of the theory first 

 propounded by Du Petit-Thouars, and more recently modified and 

 supported by Gaudichaud, which maintains, contrary to the views 

 of Mirbel and others, that aU the woody fibres of the stem proceed 

 from the nascent leaf-buds and thence descend to the radicular ex- 

 tremity of plants. Dr. AUemao believes that his observations in no 

 degree tend to support this theory. He takes as an example the 

 Cucurbita Pepo, in which the dotted vessels are extremely large and 

 conspicuous. In this plant no reticulated vessels are found in the 

 last-formed leaves or in the internodes near the termination of the 

 stem, although they exist in the lower and older leaves. He ob- 

 served spiral vessels only in the stems and leaves as low as the 9th 

 or 10th axil from the extremity of each branchlet ; from that point 

 as low as the 14th and loth axils, 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, as he believes, that all reticu- 

 lated and dotted vessels ascend through the stem before they find 

 their way into the leaves, in the progress of their growth upwards. 



