the Vasa propria, and Receptacles of the Juices of Plants. 405 



contain globules, that they coagulate by rest, and that in these 

 particulars they consequently present some features in common 

 with blood. Yet though the coloured liquids become inspissated, 

 they do not present the phenomena of blood-coagulation ; for in 

 this latter the fibrinous portion coagulates in a solid mass con- 

 taining the globules to form the clot, the other portion remain- 

 ing liquid in the form of serum ; whilst in the case of coloured 

 vegetable juices, the globules are aggregated together in a thick 

 mass, and the liquid portion evaporates. In blood, again, the 

 globules have a determinate form and a special organization ; 

 while in the proper juices of plants they are often irregular in 

 form, without organization, and of very varied composition. 

 The composition of blood is in harmony with that of the tissues 

 of animals ; it contains their elements : on the contrary, no such 

 analogy subsists between the proper juices of plants (the com- 

 position of which is very varied and complex) and the funda- 

 mental tissue of plants, constituted of cellulose. Lastly, the 

 proper juices are not found at every part, and indeed are gene- 

 rally absent from young tissues, in which the process of growth 

 principally proceeds. 



Therefore it may be said that the coloured juices of plants 

 neither resemble a fluid which has to furnish organs with the 

 materials of growth, in their physical properties, in their com- 

 position, or in the situations in which they are found. 



In the next place, are the vessels in which the proper juices 

 are contained analogous to blood-vessels? Now, it must be 

 admitted that, in certain lactescent plants, these fluids are con- 

 tained in ramifying and anastomosing vessels having simple 

 translucid walls without pores or fissures, just as Schultz has 

 represented them. To see such vessels, this observer recom- 

 mended the examination of the stipules of Ficus elastica, the 

 epidermis of which is very readily detached from the subjacent 

 tissue. On placing a portion of the tissue so prepared under 

 the microscope, the network of laticiferous vessels is at once 

 seen. If, again, of a large number of lactescent plants portions 

 be boiled, the vessels containing the coloured juices are readily 

 displayed, because the granules of those fluids are coagulated 

 into a more or less compact and continuous mass, filling the 

 tubes and rendering them very visible. By maceration for a 

 longer or shorter time, the surrounding cellular tissue becomes 

 broken up, and the ramifying tubules or vessels are left isolated 

 and open to the ready examination of their characters. Such 

 preparations may be made from the leaves, stems, or roots of 

 the plants, and among others from those of Campanula Medium, 

 C.pyramidalis, C.rapunculo'ides, Euphorbia sylvestris, E.Lathyris, 

 Cichorium Intybus, Lactuca sativa, Papaver somniferum, Ascle- 



