344 M. Lestiboudois on the Vessels of the Latex, 



produced are of smaller or larger dimensions, and anastomoses 

 occur in an irregular manner among them, whence a resemblance 

 (sufficient to cause deception) to a group of reticulated fibres is 

 set up. The appearance is that of the network of a leaf. It is 

 one of the most singular illusions that can occur under the micro- 

 scope. But it may be proved that the parts which give this 

 image of anastomotic fibres are the fissures formed in the act of 

 desiccation of the gummy fluid : some of these appear in an 

 instantaneous manner; others elongate themselves by their 

 extremity, much as fissures of glass do under the influence 

 of slight pressure. It is at times difficult to trace this forma- 

 tion, so great is the rapidity with which the dried substance 

 breaks up. But the formation of this network may be readily 

 seen by placing under ' the lens of the microscope a particle of 

 dried cortical juice, lightly breathing upon it without causing 

 displacement, and then observing it as speedily as possible. At 

 first everything is obscure, for the moisture of the breath has 

 destroyed the transparency of the glasses ; but ere long the ob- 

 jects come well into view : the moisture allows the gummy sub- 

 stance to combine in a single mass, and the subsequent desic- 

 cation reproduces a new network, altogether diS'erent from the 

 first. If we examine the cortical juice of young shoots, or of 

 the aged bark of the Acer pseudoplatanus, which contains no 

 milky fluid, all the phenomena exhibited by the limpid juice ol 

 Acer campestre are clearly shown. It therefore cannot be as- 

 serted that the limpid juices of non-lactescent plants are the 

 analogues of the coloured fluids; they have, indeed, their ana- 

 logues in lactescent plants, but not in those juices possessing a 

 special colour and peculiar qualities. We may add that the 

 tubes which enclose them do not resemble reticulated vessels ; 

 they especially occur in parts recently formed; they are thin, 

 transparent, and of variable diameter; further, they do not 

 anastomose so as to form a network, but are straight, parallel, 

 and terminate in more or less acute points placed in apposition 

 with other similar tubes, or else unite end to end, along a trans- 

 verse line, with the tubes following them. We have observed 

 similar tubes in the Vine, Antirrhinum majus, Nicotiana Taha- 

 cum, Mercurialis annua, Pelargonium zonale, Cheiranthus Cheiri, 

 Brassica oleracea, &c. 



If the tissues possessing granuliferous tubes be macerated for 

 several days, they may afterwards be easily separated, and their 

 characters be well explored. 



If they are submitted to prolonged maceration, they become 

 extensible, and are constricted by traction in such a way that 

 their cavity, at certain points, is almost completely effaced, and 

 they assume the appearance of slender threads, of which the 



