INTERCELLULAR SECRETORY RESERVOIRS. 20T 



air space, in some places as a thin layer, in others as thick masses filling the cavity, 

 while again in other places it is entirely absent. 



The intercellular spaces will be here more exactly treated, following the two main 

 categories as defined by the character of their contents. 



INTERCELLULAR SECRETORY RESERVOIRS. 



Sect. 50. Hysterogenetic reservoirs of this category arise in old masses of 

 tissue of long-lived plants from subsequent metamorphosis. Therefore, in order to 

 avoid repetition, their treatment may be passed over for the present, and be resumed 

 in Chaps. XIV and XV. We shall then speak here oi prologenetic forms only^ 



These may be distinguished by their contents, and be named as those which 

 contain resin' zxvdi ethereal oil, or mixtures of both, or Balsam; further as containing 

 mixtures qfgutn, or mucilage, or gu?n-resin. 



According to form on the one hand there may be distinguished elongated, tubular 

 canals or passages, permeating the tissues for long distances, and having a rounded or 

 angular transverse section ; and short, circumscribed, round or rather long, completely 

 closed hollows or cavities, the latter being also indicated by the word of many 

 meanings, viz. glands (comp. p. 92), and being further distinguished as internal glands, 

 to avoid confusion with the outer glands belonging to the epidermis. 



Between the general quality of the secretion and the form of the reservoir there 

 is no generally constant relation ; there are passages with balsam or mucilage, and 

 cavities with the same contents, &c. On the other hand, in both cases there is as a rule 

 a very constant, similar character of the reservoirs, according to the families, genera, 

 or species in which they occur, so that they give to these very constant anatomical 

 characters. The Coniferae are a striking exception owing to the variety of form i f 

 their resin-reservoirs in the different genera. Unimportant exceptions occur here 

 and there in other families : among the Compositse, e. g. Tagetes patula has short 

 closed sacs in the leaves, instead of the passages which are found in the other parts 

 of this plant, and in the leaves of allied species. The same holds for the leaf of 

 IVIammea americana, in contradistinction to the other parts of this tree, and the leaves 

 of other Clusiaceae. Some further cases of this sort will be mentioned in the subse- 

 quent special descriptions, p. 206. 



As already indicated, the reservoirs in question occur only in certain classes, 

 families, and genera, and especially in those which have no other places for the pro- 

 duction and storing of those secretions. A comparison of the statements in Chaps. I 

 and III will make this clear, and will also call to mind the absence of any special 

 secretory organs in the vegetative body of many plants. We may also shortly 

 mention the mutual substitution and relation of the reservoirs in question with the 

 milk-tubes in different genera and species, e. g. in the Compositae and Aroideae : this 

 has been above indicated, and will be again treated in Chap. XII. 



In rare cases a mutual substitution is found to take place between sacs and 

 cavities with the same secretion, in different parts of the same plant. This also occurs 



1 Compare Frank, /. r. — N. Mliller, in Pringsheim's Jahrb. V. p. 387. — Van Tieghem, Ann. Sci. 

 Nat. 5 ser. torn. XVI. — [Also Szyszytowicz, Sekret-behalter d. fliichtigen Oele. /i!c/. Bot. Centralbl. 

 1881, Bd. 8. p. 259.] 



