122 



PLANT ANATOMY. 



uaphthol, iu 15--20 per cent, alcoholic 

 solution, is added to the section on the 

 slule» and after 2 to 3 drops of sulphuric 

 acid have been added, if there be pres- 

 ent cano sugar, milk sugar, glucose, 

 lan-ulose, maltose or inulin, the section 

 will beeunie violet in three or four min- 

 utes. Thymol used in the same way 



FIk. 22. -Underside of Epidermis of Duboisia 

 treated with warm potassa showing precipitate 

 of alkaloid. Duboisin (Hyoscyatnin), x 350. (J, 

 20. oeller). 



Molisch's 



gives a carmine-red reaction. ^_ „ 



test is, however, not exclusive enough. 

 Orcin in a saturated alcoholic solution 

 boiled with hydrochloric acid gives an 

 orange red solution if inuliu be present. 



Aspuragin, Leucin, Tyrosin can only 

 be mentioned with aloin, quassin, san- 

 tonin and other complex chemical com- 

 pounds, which are often included under 

 the loose title of neutral principles. As- 

 paragin is of interest on account of its 

 relation to the formation of albuminoid 

 materials, it being a sort of transition 

 product in the formation of the nitro- 

 genous materials. 



Sugar in its many forms is commonly 

 found in the cell sap. As thus found its 

 most important forms are Dextrose, 

 Laevulose and Saccharose. Less often 

 Mycose, Melitose, Synanthose, Inosite 

 and Milk Sugar have been described as 

 present. 



Microchemically, Trommer's test and 

 Fehling's are to be recommended. It 

 should be borne in mind, however, that 



the tests for sugar wull react to many 

 other substances found in plant tissues, 

 such as glucosides, etc. 



Glucosldes staud in close relation to 

 sugar. They are built up of complex 

 molecules of carbon, hydrogen, oxygen 

 and sometimes nitrogen, which possess 

 the common property of being converted 

 mto glucose and other allied products by 

 the addition of weak acids or inorganic 

 ferments. Some of the more common 

 glucosides are Salicin, Solanin, Hesperi- 

 din, etc. 



Tannins are complex compounds. They 

 are found extensively in the barks of 

 plants and throughout the leaves. They 

 occur either in solution in the cell, or in 

 the form of small grains, or even in in- 

 crustations of the seed walls. 



, Fie. 23.— Cross section of Sassafras leaf show- 

 ing o. oil drops in 02:. suberized oil cell, ep. epi- 

 dermis, p. Palisade cells. (Tschirch). 



Alkaloids. "Under this heading is gen- 

 erally included a large number of natu- 

 ral basic compounds which are nitrogen- 

 ous and which give certain characteris- 

 tic chemical reactions. They are prob- 

 ably products of destructive metabolism 

 and are found in the cell sap. They 

 generally rich in the meristematic tis- 

 sues, but their exact locality is still in 

 doubt. It is probable tbat in an unal- 

 tered condition alkaloids are not to be 

 detected by the microscope. By means 

 of micro-chemical tests, however, many 

 have been isolated and studied. In 

 many cases the active medicinal princi- 

 ples depend upon alkaloids, as in Mor- 

 phine, Strychnine, Physostigmlne, etc. 

 Many of the alkaloids are highly poi- 



