274 M. Lestiboudois on the laticiferous Vessels of Plants. 



so that these granules, particularly those of considerable magni- 

 tude, appear to be constituted of a multitude of others of extreme 

 tenuity. When the granules are allowed to dry upon the glass 

 slide, they at times continue distinct, and retain their globular 

 aspect ; but, on the other hand, they often collapse and spread 

 out, uniting together to form films, excessively thin and trans- 

 parent, and singularly irregular. On dropping tincture of iodine 

 upon a slice of cortical tissue, this agent quickly removes nu- 

 merous granules of the milky fluid which were contained in the 

 lacunae. The largest number of the cells become coloured blue as 

 well before as after boiling, although this process causes the disap- 

 pearance of the starch-corpuscles by transforming them into an 

 amorphous mass. There are nevertheless certain cells which are 

 not so coloured by the iodine, but contain a yellowish granular 

 matter. The elongated cells are either empty or contain a few 

 yellowish granules. Hence, in the Sumach, the coloured juices 

 may be contained in cells, and are certainly met with distributed 

 in the lacunae ; these latter are met with as well in the root as in the 

 stem, and are sometimes regular like vessels, but at other times 

 less distinctly defined and less uniformly cylindrical. The milky 

 ]\x\c& oi Acer platanoides is likewise composed of rounded gra- 

 nules capable of coalescing and of forming regular or irregular 

 spots when allowed to dry upon a glass slide. Lastly, there are 

 plants, such as certain Euphorbia, the proper juices of which 

 become extravasated, and occupy irregular lacunse formed by 

 the laceration of the tissues. 



It follows from what has been stated, that the proper juices 

 of plants are enclosed within reservoirs of widely different struc- 

 ture, which may constitute vessels, or cells, or channels (meati), or 

 lacunae. Those which must be looked upon as vessels are some- 

 times long, rigid, thick tubules, without anastomoses, or with 

 few intercommunicating branches ; whilst at other times they 

 are thin, flexuose, and branching, with frequent inosculations, 

 and form a more or less delicate network ; they present, more- 

 over, at times constrictions here and there, sometimes joints 

 without septa, and at others articulations with septa. Those 

 reservoirs which are nothing more than utricles retain in certain 

 plants a vascular appearance, by reason of the grouping of the 

 cells in linear series more or less marked. Further, these cells 

 are either short or elongated, regular or irregular, thin or fur- 

 nished with firm and thick walls. In other plants the cells are 

 collected so as to form rounded masses, of very variable figure, 

 making no approach in appearance to a series of vessels. The 

 reservoirs which are intercellular passages (meati) present them- 

 selves in the form of slightly branching vessels, constituting 

 now and then a sort of framework around cells. Those which 



