76 VEGETABLE HISTOLOGY. 



GINGER KHIZOME. Cut cross-sections from the dry rhizome, 

 mount a thin one in water and examine with low power first. 

 The section is made up for the most part of large starch grains 

 in ordinary parenchyma cells, but here and there may be seen 

 groups of thick-walled light yellow cells, the fibres and vessels 

 of the wood bundles. In addition to these there will be seen 

 more or less distinctly lighter or darker yellowish homogeneous 

 masses. They are the oleo-resinous contents of secretion sacs 

 which are scattered over the whole section. If dilute iodine 

 solution be added the section turns dark, but the groups of 

 woody cells now stand out more conspicuously in contrast by 

 their deep yellow walls and the resin sacs also. 



Fig. 46. Cross-section of Ginger rhizome showing a vascular bundle and paren- 

 chyma ; oil, oleoresin sacs; scl. f., bast fibres; v, wood vessel (Vogl). 



To remove the starch grains which interfere by their great 

 numbers mount a section in chloral hydrate solution and warm 

 gently. The shape of the parenchyma, wood bundles and the 

 secretion sacs can now be seen more easily. 



Mount a section in caustic alkali (5 per cent.). The starch 

 dissolves and the secretion sacs turn a deep reddish-brown, 

 because of the union of alkali with the resin. In the liquid of 

 the sacs unchanged oil drops are visible. Use high power also 

 in the above experiments and also study the starch grains 

 carefully. 



MUCILAGE SACS IN MARSH-MALLOW KOOT. 



Wrap a piece of the root in wet filter paper until it is soft 

 enough to cut. Make cross-sections and place them in dilute 



