342 M. Lestiboudois on the Vessels of the Latex, 



life : they exist or are absent in tbe most intimately allied spe- 

 cies j they are wanting in the most important organs ; they are 

 enclosed in reservoirs of entirely different structure. There are 

 certainly some vessels which appear articulated, because the 

 constrictions they present extend so as to constitute septa, or 

 because, when they are observed, they are broken into several 

 pieces — a circumstance which happens because the reservoirs 

 are originally constituted of cells united end to end. There are 

 some which occur in the form of irregular masses ; such there- 

 fore cannot be regarded as having primitively formed vessels. 



These facts being beyond dispute, the opinion has been put 

 forward that it is necessary to distinguish the coloured liquids 

 enclosed within vessels from those contained in cells, meati, and 

 lacunse, and that the former alone constitute the nutritive juice 

 and have their analogues in all plants. This brings us to the 

 examination of the fifth and sixth questions we have propounded, 

 and leads us to inquire, in the first instance, whether, in fact, 

 two distinct categories of coloured juices can be instituted. 



At any rate, no character can be seized upon which will 

 serve to establish a line of demarcation between them : often the 

 juices which are contained in vessels differ more among them- 

 selves in composition than they do from those which are found 

 in cells. Some juices contain fatty matters, others substances of a 

 totally different nature, such as caoutchouc ; some are bland and 

 nutritious, others are acrid and poisonous ; some possess alka- 

 loids endowed with energetic properties, others contain no such 

 compound principles. No greater differences are met with be- 

 tween the liquids contained in different reservoirs. If, therefore, 

 no indication can be discovered, sufficient to distinguish one 

 from the other, on what grounds, it may be asked, can it be 

 asserted that some are special, secreted, excrementitial juices, 

 and others of the nature of vital and of alimentary fluids ? Such 

 a distinction is assuredly too arbitrary. 



It can with still less reason be admitted in certain plants, 

 such as Chelidonium, previously cited, — where the coloured juices 

 of the stem are contained in vessels, whilst those of the root are 

 enclosed in cells. These juices preserve their properties in their 

 integrity, although their receptacles differ in form and may 

 assume the numerous configurations which are peculiar to ve- 

 getable tissues. 



We have now to inquire whether it is true that in all non- 

 lactescent plants there are vessels which constitute a capillary 

 network such as M. Schultz has described and figured, differing 

 only from lactescent vessels by reason of their fluid contents 

 being limpid instead of coloured. In instituting this inquiry we 

 encounter the most important of the problems to be solved ; for 



