2G PRACTICAL BOTANY. 



Treat with alcohol ; the green colouring matter 

 (chlorophyll) is gradually dissolved out, and the 

 corpuscle is left colourless. 



Press out the contents of an internodal cell of Nitella 

 or of Cham on a slide ; put on a cover-slip and examine 

 with a high power. Run in some distilled water : 

 observe that the corpuscles swell up, assuming the 

 form of large hyaline vesicles ; the chlorophyll is con- 

 fined usually to one portion of the vesicle. 



If chlorophyll-corpuscles, which have been treated 

 with picric acid and decolorised with alcohol, be stained 

 with iodine, Hoffmann's blue, or hsematoxylin, and be 

 examined with a very high power, it will be seen that 

 they have a trabecular structure ; it is from the inter- 

 stices of the trabeculaB that the colouring-matter has 

 been removed. The leaves of Vallisneria afford good 

 material. 



The same result may be obtained by prolonged treatment with 

 dilute acid (hydrochloric acid mixed with water in the proportion 

 of 1 : 4, is most effectual), or by exposure for one or more hours 

 to steam (Pringsheim). 



The minute structure of the corpuscles can be very 

 readily made out in cells of the leaves of JEcheveria. 



If the plants used have been previously exposed to 

 light, it will be observed that the chlorophyll-corpuscles 

 contain granules. If a decolorised corpuscle be treated 

 with iodine, the inclosed granules will turn blue, showing 

 that they are starch -granules (see p. 33). 



b. Leukoplastids. These are colourless protoplasmic 

 corpuscles of various shape, which are to be found in 

 the cells of those parts of plants which are not exposed 

 to light, and in which starch is deposited. 



