130 PRACTICAL BOTANY 



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. 



() Cane-sugar. 



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

 water, and note under a low power the transparent tissue, and 

 coloured cell-sap. Treat such a section for a few minutes with 

 alcohol in a watch-glass : on re-examination under the micro- 

 scope, 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 small bulk 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 sections as 

 directed above : no precipitate will be formed either in the 

 cells or in the surrounding fluid. 



IV. Oil-drops. 



Cut thin sections of the cotyledons of the Almond : mount in 

 water, and note the bright-looking oil-drops, both in and about 

 the section, and dispersed also in the water. 



1. Irrigate with alcohol : the drops are not dissolved. 



2. Treat a section with a considerable bulk of ether in a 

 watch-glass : wash with alcohol, and mount in alcohol, or 

 in glycerine : on examination the oil will be found to have been 

 dissolved by the ether. 



3. Stain a thin section with tincture of alkanet (see Appendix 

 A), the oil-globules stain pink. 



4. Treat a section with i per cent, solution of osmic acid : 

 the oil-drops will stain slowly, taking a dusky or black hue. 



5. Treat a section with potash solution, and warm : the oil 

 will be partially and slowly saponified and dissolved. This 

 effect of potash is best seen in specimens where the oil is 

 present only in small quantities as isolated globules. 



V. Aleurone-grains. 



These are found of the largest size in oily seeds : they vary 



