.1/ /N U TE UTR UC TUlii: 



these, unlike cliloi-opli.N II, are iirocluceJ in daikness as 

 well as in sunlight. 



Chlorophyll is of the utmost importance to the plant, seeing 

 that only in the cells which contain it. and in tlio pros- 

 euce of sunlight, can the materials whi<-h the j.Iant 

 imbibes from the soil and the air be tiNsimildted. that is, 

 converted into matter wliiih the plant can use for the 

 purposes of growth. 



Now consider Fig. 2")!. Here are exhibited cell-contents of 

 an entirely different aspect. The rounded bodies here 

 \\?,'\h\e a.YQ starch-(jranuli's. as may be easily demonstrated 

 by adding a drop of iodine solution to the Potato section 

 under the microscope, a characteristic blue colour being 

 at once produced. Such granules, differing somewhat in 

 shape in different cases, abound in the cells of tu1)crs and 

 grains of all sorts, where they have been stored up for 

 use during the process of germination. Thej^ are origin- 

 ally formed during sunlight in the chlorojihyll granules 

 of the green parts. "When the light is withdrawn, as at 

 night, they are dissolved and carried in solution to other 

 parts to promote growth or to be stored up. If starcli- 

 granules are subjected for a time to the action of saliva 

 it will be found that a portion of each granule has been 

 dissolved out, leaving an insoluble skeleton behind. The 

 granule is thus shown to be made uj) of two distinct parts, 

 the more soluble portion being known as yranulosr, and 

 the less soluble framework as starch-cellulose. 



Crystals. 



These are of common occurrence in many plants, not o\\\y in 

 the cell-cavities, but also imbedded in the substance of 

 the cell-wall. They are also of various shapes, and may 

 either occur separately or be massed together in clusters. 

 The needle-shaped forms are known as vaphidis. Tlie.se 

 crystals consist for the most part of calcium oxalate, but 

 calcium carbonate is- also found, and may be readily dis- 

 tinguished from the former by the effervescence occasioned 

 on the addition of h\drochloric acid. The oxalate dis- 

 solves in this acid without effervescence. 



Crystals may be readily observed under the microscoiie in thin 

 sections of scales from the Onion bulb (Fig. 2()9), Khu- 

 barb, Indian Turnip, and many other plants. 



In the leaves of plants of the Nettle Family it fretiuentl^- hap- 

 pens that a wart-like growth of celhdose takes i)lace 

 on the inside of the cell-wall, the inwardly projecting 

 mass being attached to the wall by a slender stalk, and 

 having multitudes of small crystals imliedded in it. Such 

 inward growths are called cijstoliths ; they may be 

 readilv seen in cross-sections of the Nettle leaf. 



