ELEMENTARY STRUCTURE. 



55 



the Coniferre they contain turpentine, and ha^-e therefore been 

 termed turpentine vessels. They occur in such plants in the 

 wood, bark, and other parts; those in the wood are elongated 

 tubular passages. In the rind of the fruit of Umbelliferous 

 Plants they form club-shaped receptacles of oil, which are 

 commonly "^ termed vittce {fig. 136). These receptacles are 



Fig. 136. 



Fig. 13G. Fruit of Parsnip (Pasfinaca sativa) a. Dorsal surface, h. Hori- 

 zontal section of the fruit. a,b,b,c,c. Primary ridges. 1,2,3,4,5,6. 

 Vittae. 



found especially in certain orders of plants, to which they com- 

 municate important properties. 



Intercellular Substance. — The spaces above described as occur- 

 ring between the sides of cells, appear in some few cases to be 

 filled up by solid matter, to which the name of intercellular sub- 

 stance has been given. This appears to be of the nature of 

 cuticle, and in some instances, as we haA^e seen, it is in connexion 

 with that structure through the orifices of the stomata, forming 

 with it the so called p- ^37^ jp- ^gg^ 



cistome, (see p. 41). 

 Formerly this inter- 

 cellular substance was 

 supposed to be uni- 

 versally distributed be- 

 tween the cells glue- 

 ing them together as 

 it were, and in some 

 plants occurring in 

 great abundance; as 



in mnn-i' Alo-<v. tViA ^^O' '^^'- Section of the alhumen of tlie seed of 



in man} Algre, the Betel-Nut Palm (Areca Catechu). 



hornv albumen of Fig. laS. Tlie same, after treatment with sulphuric 



seeds, between the -'l and iodine. After Hentrey. 



collenchymatous cells of the common Beet, Sec. In these cases 

 the intercellular substance has now been proved to consist 

 really of secondary deposits inside the cells, as may be seen 



E 4 



