CHAP, xvii.] OF SECRETION AND EXCRETION IN GENERAL. 257 



that is to say the kidneys and the sudoriparous glands. The 

 salivary glands and the liver represent well t'he glands of the 

 second type. 



The higher the perfection of an organised being the more its 

 organs of excretion and secretion are numerous and specialised. 

 From this general proposition, applicable moreover to all organic 

 apparatus, we may infer that the organs of elimination are very 

 rudimentary in the vegetal kingdom. Lacking there completely 

 are the complex glandular organs, furnished with canals of dis- 

 charge, such as exist in animals. We might bring the vegetal 

 glands into relation with the glands closed or without the excretory 

 conduits of animals. In both cases, in effect, the secretory organ 

 is represented by cells elaborating at the expense of the nutritive 

 liquids special substances, which come forth from the cells, either 

 by exosmosis or by rupture of the cells which have formed them, 

 but are not then received into special conduits ; for the network, 

 called network of secretion, into which is poured the essential 

 oil of the helianthus, the resinous gum of certain umbelliferse, 

 the limpid balm of the conifers and the terebinthaceae, is merely 

 composed of meatus more or less ramified, due to simple ecarte- 

 ments of cells. 



The secreting cells of vegetals are sometimes isolated and 

 sometimes grouped. As example of the first we may cite the 

 spherical cell, filled with a viscous or odorous substance, which 

 terminates certain vegetal hairs. Other glandular cells, isolated, 

 are dispersed over the parenchyma of the tissues, for instance the 

 camphoric cells of the leaves of the CampJiora officinarum. Often 

 the glandular cells are grouped in small masses, for instance, that 

 which contains the essential odoriferous oil in the rind cf the 

 citron. Sometimes the walls of these cells open or are reabsorbed, 

 and the place they occupied is transformed into a reservoir. But 

 these are special secretions. As to the form under which are 

 eliminated the products of disassimilation of the plant, it is 

 still very little known. Must we regard as products of excretion 

 the matters resinous, cereous, or slimy, and so on, which are 



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