CHAPTER III. 



SECRETORY RESERVOIRS. 



Sect. 31. Bodies of a nature similar to the secretions of the dermal glands 

 (Sect. 19), such as mucilage, and gum, resin, ethereal oils, and mixtures of these 

 designated balsam, milky emulsions of the bodies of both categories which are 

 known in the dry state as ' Gum-resins,' are often found laid by in the interior of the 

 tissues; they occur on the one hand in special Sacs, which develope during the 

 differentiation of tissues from definite cells of the meristem : these, retaining their 

 membrane, and growing considerably, are filled completely with the bodies in ques- 

 tion, and thereby lose their original cell-nature ; or they are found in special hiter- 

 cellular spaces. 



There occur in many plants other sacs, arranged similarly to the above, which 

 also arise with the first differentiation of tissue from cells of the meristem, and con- 

 tain as their sole or preponderating contents crystals of oxalate of lime. All these 

 places of secretion or reservoirs are closely related to one another. The aggrega- 

 tions of crystals are often associated with large deposits of mucilage in the cavity of 

 a sac, so that one may speak of mucilage-sacs with crystals (e.g. tubers of orchids) 

 or of crystal-sacs with mucilage (e.g. Raphide-bearing sacs), according to the pre- 

 ponderance of one or the other body. 



As already stated, resin and mucilage often occur mixed together. The form 

 of the sacs merges not uncommonly into that of intercellular spaces filled with the 

 secretory mass, since rows or groups of the former, by absorption of their walls, 

 coalesce to an amorphous intercellular mass. Further, sacs and intercellular spaces 

 with like contents often mutually replace each other, since, in the first place, the 

 same body in different members of the same plant sometimes fills sacs, at other 

 times intercellular spaces, e.g. the red resin of species of Lysimachia and INIyrsine ; 

 or secondly, of closely allied plants some have sacs, others intercellular spaces filled 

 with the same secretion, at the same points. Examples of this will be found 

 below, among the Coniferse, Compositae, &c. Finally, in families more remote from 

 one another, there occurs only one or the other form of secretion and of the reservoir 

 containing it. 



The mode of formation of the secretion in the interstitial dermal-glands cor- 

 responds closely with that of the schizogenetic resin-passages, which are to be 

 described below. We must here refer especially to the depressed glands of Psoralea. 



In consideration of its known properties, calcium oxalate can only be regarded 

 as a' body, which is removed from the metastasis of the plant, and is secreted or 



