40 



THE VEGETABLE CELL IN GEMEKAL. 



appear to be much like the sphere-crjstals described in 18G. But 

 if they are carefull}- treated with dilute lydrochloric acid, the 

 chief part of the concretion disappears, leaving behind a delicate 

 trace of cellulose which was intermingled 

 with it. That this cellulose was an in- 

 trusive growth into the cell from the 

 wall, is shown bj- a studj' of its develop- 

 ment. In most cases such concretions 

 (C.vstoliths) are plainly- stalked, but in 

 some instances thej' are onl}- obscurely 

 stalked, and are with difflcultj- distin- 

 guished from the ordinary cell concre- 

 tions. In the leaf of Ficus elastica (see 

 Fig. 6) the}- are more completely devel- 

 oped than in any other common plant. 



165. Otiier changes, chiefly those of 

 degradation, maj- take place in the cell- 

 viall, giving rise to products varfously 

 known as gums, resins, &c. ; but in all these cases there is such 

 a commingling of the cellulose derivatives with those formed 

 from the contents of the cell, that they cannot be readily dis- 

 tinguished. 



166. Protoplasm, as was shown in the previous sections, gives 

 rise upon its exterior to the cell-wall. Inside the cell, likewise, 

 it produces, either directly or indirectlj-, various substances. In 

 the present chapter these substances are to be considered onlj- so 

 far as relates to their detection and identification. Most of them 

 are to be examined later, with reference to their office in the life 

 of plants. 



167. Plastids. In the protoplasm of active cells certain gran- 

 ules having substantially the same chemical and, with the excep- 

 tion of their color, the same physical properties as protoplasm, 

 are clearly differentiated. They are imbedded in the general 

 protoplasmic mass, and are not separable from it b^- mechanical 

 means. 



168. Such grannies may be convenientlj' referred to three 

 tj'pes,' depending upon the color : (1) those which are green, — 



1 Recent investigations render It probable that these three kinds of granules 

 are derived fi'om a common source, and although hardly distinguishable from 



Fio. 6. Cystolitli from the upper part of a leaf of Ficns elastica. e, epidermis; 

 /i, liypoderma; cCy cystolitli; ch, ch, cells containing cMorophyll. It will be observed 

 that the pedicel of the cystolith appears to be attached to the lower wall of the upper 

 epidermal cells. 



