98 



MOllPHOLOGY OF THE CELL. 



one or more essential oils, forming a thickisL liquid ; (2) Itesins, 

 which hiivc comparatively little essential oil commingled, and are 

 of various grades of hardness ; (3) Gum-resins, or resins hav- 

 ing more or less mucilaginous or gummy matters. To the latter 

 class are sometimes referred 

 the products left by the drying 



of many milk}' juices (latex) ; of such, caoutchouc is an ex- 

 ample. All the foregoing substances may be found in single 

 cells, which are of very diverse forms. 



296. Roundish cells of this character are found in the Mag- 

 noliacese and some Compositte, etc. Long cells are to be de- 

 tected in some Liliaceae, etc., and thej' are connected hy many 

 intermediate forms with resin-ducts arising from the confluence 

 of several cells. On tiie other hand, they pass by various gra- 

 dations into structures which are generally referred to the latex- 



FiG. 79. Transverse section tlirongh tlie leaf of Psoralea liirta ; tlie epiilermis con- 

 sisting of one layer with some of tlie tissue shown on both sides of (he glanil: J, very 

 young state in wliioh the secretion is not yet present; B, somewhat older, secretion 

 commencing; (? mature state. (DcBary.) 



Fig. SO. A "gland" in Diotiimnus Fraxinella : .4, £, early stages; C, mature state; 

 p,p, c, motlier-oella of tl.e gland-tissue; (J, the covering layer forming a continuation ot 

 the epidermis; o, a large drop of oil. (Rauter.) 



