222 PRACTICAL BOTANY 



Irrigate thoroughly with water : the crystals may be 

 seen to be re-dissolved : they consist of grape-sugar, 

 which is in solution in the cell-sap of the living cell. 



2. Squeeze out the juice of some Grapes into a test- 

 tube : add a little of Fehling's solution (see Appendix A), 

 and boil : a bulky yellow precipitate is formed owing to 

 reduction of the copper. 



3. Soak a fairly thin section of a Grape in Fehling's 

 solution : wash quickly with water, mount in water, and 

 boil gently over a spirit-lamp : a precipitate like the 

 above (2) is formed : note under the microscope that the 

 dark-looking granules of the precipitate (cuprous oxide) 

 are to be found actually within the cells of the tissue, 

 thus indicating that the sugar was there. 



(b) Cane-sugar. 



1. Cut transverse sections of the Beet-root : mount 

 them in water, and note under a low power the trans- 

 parent tissue, and coloured cell-sap. Treat such a 

 section for a few minutes with alcohol in a watch-glass : 

 on re-examination under the microscope, crystals will 

 be seen in the cells, but of smaller size than in the 

 Grape. Re-dissolve by irrigation with water. 



2. Boil some small pieces of Beet-root in a smalLbulk 

 of water : pour off the coloured extract, add to it a little 

 of Fehling's solution, and boil : no precipitate will be 

 formed. 



3. This point may be further verified by testing sec- 

 tions as directed above, under head (3) : no precipitate 

 will be formed either in the cells or in the surrounding 

 fluid. 



V. Oil-drops. 



Cut thin sections of the cotyledons of the Almond ; 



