the Vasa propria, and Receptacles of the Juices of Plants. 34:7 



elastica, a semicircle of transparent small points may be seen 

 beneath the inferior bundles of the petiole and above the superior 

 ones. 



In most plants the tissue enclosing the cortical tubes may be 

 easily separated from the spiral vessels, and the pi'oper vessels 

 be readily and distinctly demonstrated. It must therefore be 

 supposed that they represent an entirely diflferent histological 

 constituent, and the more so because we know that the liquids 

 they contain are also of a different character. 



We therefore conclude that the tubes met with in the greater 

 number of plants, enclosing transparent and granular fluids, 

 have not the structure of proper vessels : they are not ramified ; 

 they do not anastomose and form a network ; they are, on the 

 contrary, analogous to fibrous tubules, and shade off into them ; 

 they occupy the same position ; their walls are proportionately 

 thicker as they grow older ; they are straight, simple, aggregated 

 in bundles, and have acute or rectangular extremities placed in 

 apposition with those of similar tubes so as to form filaments or 

 fibres, but not a vascular system or network ; lastly, they all 

 contain the same sort of fluid. They occur not only in non- 

 lactescent plants, but also in those possessing coloured juices 

 and vessels. They must therefore be regarded as distinct from 

 the last-named reservoirs. They constitute the commencement 

 of fibrous tubes, shade off into them, and progressively assume 

 all their characters. 



We do not go so far as to assert that vessels anastomosing to 

 form a network, and containing granular uncoloured juices, are 

 never to be met with. The immense varieties of vegetable pro- 

 ducts justify the belief that the juices contained in the vessels 

 need not necessarily be always coloured by the granules they 

 hold in suspension ; indeed it is a fact, remarked in the case of 

 certain lactescent plants, natives of tropical climates, that the 

 coloured juices are absent from them when grown in our climate; 

 that is, they fail to secrete, under the influence of a lower 

 temperature, those juices marked by a higher degree of elabora- 

 tion. Nevertheless they retain the special apparatus belonging 

 to them, and the only change is that the liquids they contain 

 do not possess those properties that they would have acquired 

 had their vital activity been sustained in full vigour. The cir- 

 cumstance we have sought to show is, that the tubes of plants 

 normally devoid of coloured juices do not seem the analogues of 

 proper vessels. 



In our opinion, therefore, it is sufficiently demonstrated that 

 a vascular system like that existing in animals, concerned in 

 transporting and distributing the nutritive juices prepared by 

 special organs, is not found in plants : the proper vessels them- 



23* 



