108 VEGETABLE ORGANOGRAPHY. 



It appears from tlie admirable observations of Bern- 

 hardi, Mirbel, and Treviranus, npon this subject, that the 

 Proper Juices have no perceptible motion, and that they 

 only come out of the plant when the envelopes which 

 shut them up are broken. These envelopes are, in 

 general, thicker and firmer than those of Lymphatic 

 Vessels ; they are always devoid of every kind of dots or 

 rings, so that they are easily known by this character 

 when they are beheld under the microscope. They are 

 better distinguished by their generally being of a larger 

 diameter than true vessels, and especially in not having 

 such regular forms, and from the walls which enclose 

 them not appearing to belong to them : it seems, as 

 Grew has indicated, that the Proper Juices, secreted 

 in certain parts by glands or membranes as yet 

 unknown, are deposited in the neighbouring cellular 

 tissue, distending or breaking it ; and there form round 

 or elongated cavities, which have a vascular appearance, 

 but which, as is seen, differ entirely from vessels : by 

 this hypothesis, they would be true cystous sacs, very 

 analogous, for instance, to those which form encysted 

 aneurisms in animals. 



Link has given them the name of Receptacles 

 OF Proper Juice (receptacula sued jjrojpriij, 

 which exactly suits them, and which ought to be 

 adopted in order to separate these organs from true 

 vessels. 



In considering the different forms which the Re- 

 ceptacles of Proper Juices present, we may arrange 

 them in several classes : — 



1st. Vesicular Receptacles (reservoirs vesicu- 

 laires), which are those which authors have called 

 Vesicular Glands ; that is to say, those nearly spherical 

 vesicles situated in the tissue of leaves, — as we see in 

 the Myrtle, or the rind of the Orange, &c. These 



