96 MORPHOLOGY OF THE CELL. 



forded by the following orders, Asclepiadaceae, Apocynacese, 

 and Euphorbiacese. 



The complex forms consist of rows of cells which coalesce to 

 form a latex-system. The individual cells may have their parti- 

 tion-walls broken down very early, a mere vestige of them remain- 

 ing ; or the partitions may be simply perforated, so as to allow a 

 free communication between contiguous cells. Moreover, the 

 confluent cells may be conjoined laterally, thus constituting a 

 complicated network which runs through the plant. 



288. Occasionally roundish groups of perforations resembling 

 in a few particulars those of sieve-plates are found in the latex- 

 cells of Papaver and some Cichoracere ; but they are coarser and 

 more irregular, and are devoid of the peculiar sieve-plate struc- 

 ture. Moreover, no true intermediate forms have been proved 

 to exist between the two kinds. 1 



289. The wall of a latex-cell is often very thin, and free from 

 any markings ; but with even slight increase of thickness, stria- 

 tions and stratification make their appearance, projections may 

 extend into the cavity of the cell, or even spirals may be present. 

 In character, the cell-wall possesses many of the peculiarities of 

 collenclryma, especially in its behavior w r ith iodine. 



290. That the cells contain a protoplasmic lining is highly 

 probable, but this has not yet been satisfactorily demonstrated. 

 The liquid in the cells consists of granular matters suspended in 

 a watery fluid, and imparting to it a milky appearance. Often 

 the color of the liquid is yellow, as in Argemone, or orange, as in 

 Chelidonium. The wateiy fluid contains in solution sugar, gums, 

 resins, traces of albuminoid matters, and various principles, for 

 instance, alkaloids (like morphia), and organic acids. 



The suspended matters are of minute size, with the excep- 

 tion of peculiar forms of starch-granules. When perforation 

 is made in the latex-system of a turgescent stem, these granules 

 can lie seen to move towards the point of injury. The same 

 movement can be observed when the pressure on one part of 

 the stem is materially increased ; and hence arose the erroneous 

 belief that there is a circulation of latex. 2 



291. Upon exposure to the air latex coagulates, and forms 

 upon drying a stick}', elastic mass, which in some plants is suffi- 

 ciently abundant to furnish the india-rubber of commerce. 



1 D. H. Scott : On the development of artirnl;ted laticifeions vessels. 

 Journ. Mic. Science, 1882, p. 144. An interesting account is also given by 

 de Bary, from notes by Schmalliausen, Vergleichende Anatomic, p. 205. 



2 Schultz : Die Cyklose des Lebmssnftcs in den Pflanzen, 1841, p. 282. 



