VESSELS OF THE LATEX. 



49 



63. laticiferous Tissue. {Vessels of the Latex or Milky Juice. 



\ Oinenchyma of Morren and Lindley.) This consists of long and 

 irregular branching tubes or passages, lying in no definite position 

 with respect to other tissue, and when young of such extreme tenu- 

 ity (their average diameter being less than the fourteen-hundredth 

 of an inch) and of such trans- 

 parency that they are hardly 

 visible, even under powerful mi- 

 croscopes, except by particular 

 manipulation. But their older 

 trunks are larger and more evi- 

 dent, when gorged with the milky 

 or other special juices which it is 

 their office to contain, and when 

 their sides are thickened by 

 the deposition of such matters. 

 Another peculiarity is, that they anastomose or inosculate, forming 

 a sort of network by the union of their branches, so that they freely 

 communicate with each other. In this respect, as well probably as 

 in the mode of their formation, they resemble the veins of animals.. 

 But their branches do not proceed from larger trunks, and in turn, 

 divide into smaller branchlets. They merely fork and inosculate' 

 here and there, the branches being commonly as large as the trunk 

 before division. Tlie articulations which they often present (as in 

 the upper part of Fig. 67) would seem to prove that they are formed 

 by the confluence of cylindrical cells. It is altogether most probable, 

 however, that they are not composed of cells at all ; but are, at first,, 

 mere passages in the intercellular spaces, which in time are bounded 

 by walls formed by deposition from the contained fiuid. Schultz, 

 who discovered these peculiar vessels and gave to them their present 

 name, describes a regular circulation of the juice they contain; 

 which would make them still more analogous to the vessels or veins 

 of animals. But this has been shown to have no real! existence. 

 There is merely a mechanical flow from any part under pressure, or 

 towards a place from which the latex is escaping, as from a wound.. 



\ Laticiferous vessels occur in the bark, especially in the liber, in the 

 leafstalks, and in the leaves, especially of those plants which have 

 a milky juice. 



FIG, 66. Vessels of the latex, ramifying among cellular tissue, in the Dandelion ; and 67, . 

 older and larger vessels from the same plant ; all highly magnified. 



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