18 
PLANT MORPHOLOGY. 
whereas, if a little water is added and the trituration 
repeated, a deep blue color is immediately produced. 
The blue color of starch solution and iodine disap- 
pears on the application of heat, but slowly returns on 
cooling the solution, but not with the same degree of 
intensity. 
When starch is heated with glycerin it dissolves, and 
if alcohol is added to the solution, a granular precipi- 
tate is formed which is soluble in water, the solution 
giving a blue reaction with iodine. 
When starch is heated with an excess of water at 
100° C. for varying periods of time, it completely dis- 
solves with the formation, first, of soluble starch, which 
gives the characteristic blue reaction with iodine; then 
the production of dextrin compounds, giving violet- 
red, reddish and yellowish reactions with iodine ; 
finally, maltose and dextrose are produced, these giv- 
ing no reaction with iodine, but reducing Fehling’s 
solution. The ferments and dilute acids have a simi- 
lar effect on starch. The dry heating of starch at 
temperatures of 150°-170° C. changes it to dextrin. 
VEGETABLE DRUGS CONTAINING STARCH. 
The more important vegetable drugs, including some 
of the commercial starches, are here grouped according 
to the size and shape, or other peculiarities, of the 
starch grains : 
SIMPLE SPHERICAL GRAINS. 
(1) Those not more than 5 /x in diameter: Cimicifuga, 1 cypripe- 
dium, frangula, hydrastis, leptandra, piper, prunus virginiana, 
quassia, quercus alba, rhamnus purshiana, spigelia, viburnum 
opulus and viburnum prunifolium. 
(2) Those not more than 10 /x in diameter : Calamus, euonymus, 
gelsemium, granatum, quillaja, sanguinaria, serpentaria, tonka, 
ulmus, xanthoxylum. 
1 See Plant Names in Introductory to Part II. 
