96 MORPHOLOGY OF THE CELL. 



forded b}' tbe following orders, — Asclepiadaceae, Apocynacese, 

 and EiiphorbiaceiE. 



The complex forms consist of rows of cells which coalesce to 

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

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

 ing ; or the partitions maj' be simplj- perforated, so as to allow a 

 free communication between contiguous cells. Moreover, the 

 confluent cells may be conjoined laterall3', 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 Cichoraceee ; but the}- 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.' 



289. The wall of a latex-cell is often verj- 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 m.inj- of the peculiarities of 

 coUenchyma, especiall}- in its behavior with iodine. 



290. Tliat 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. Tiie watery fluid contains in solution sugar, gums, 

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

 instance, alkaloids (like mor[)hia), 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 be seen to move towards the point of injury. The same 

 movement can be obscjved 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.^ 



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

 upon drying a sticky, 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 articulnted laticiferous vessels. 

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

 de Bary, from notes by Schmalliansen, Verglelchende Anatomie, p. 20,5. 



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



