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1 8. Tannins. Tannins are amorphous substances occurring in
plants having an astringent taste, and turning dark blue or green
with iron salts. They occur in greatest quantity in the bark of
exogens, and in gall formations. They are soluble in water, alcohol
glycerine, and a mixture of alcohol and ether. They are almost
insoluble in absolute ether and chloroform. They give insoluble
precipitates with organic bases such as alkaloids and with most of
the salts of the heavy metals.
According to their behavior with solution of iron chloride or
other soluble iron salts two kinds of tannic acid are recognized: (a)
a form of tannic acid giving a blue color, as that which is found in
Rhus, Castanea, Granatum, Galla, etc.; (b) another tannic acid
producing a green coloration, as that found Buy Avapro Online in Krameria, Kino,
Mangrove bark, Quercus, Catechu, etc.
If sections are placed in a 7 per cent, solution of copper acetate
for a week or more, then placed on a slide in 0.5 per cent, aqueous
solution of ferric chloride, and after a while washed with water and
mounted in glycerin, an insoluble brownish precipitate will be pro-
duced in those cells containing tannin.
19. Proteins. Proteins are complex nitrogenous substances
forming the most important of the reserve foods of plants. They are
found in all the living and many of the dead cells of plants, although
most abundant in seeds. Protoplasm, itself, is composed largely
of these substances. They all contain carbon, hydrogen, oxygen,
nitrogen and sulphur, and Buy Avapro Online many contain in addition phosphorus.
They are formed by the addition of nitrogen, sulphur and fre-
quently phosphorus to elements of grape sugar. The nitrogen,
sulphur and phosphorous elements are obtained from nitrates,
sulphates and phosphates which are dissolved in the water taken
in through the roots. The names of proteins recorded may be
found by the hundreds. These are grouped into chemical classes,
the most important of which from the standpoint of their occurrence
in plants are the globulins, albumens, glutelins, nudeins, and gliadins.
Of these the globulins are found most extensively. Globulins are
insoluble in water but soluble in sodium chloride solutions. They
do not coagulate upon the application of heat. Buy Avapro Online
Albumens are soluble in water and coagulate with heat.
Glutelins are insoluble in water, sodium chloride solution and
Gliadins are nearly or wholly insoluble in water but soluble in
70 to 90 per cent, alcohol.
Nucleins are insoluble in water but soluble in akaline solutions.
The following tests are of value in determining the presence of
Lugol's solution stains proteins yellow or brown.
Concentrated nitric acid stains proteins yellow. This color
becomes deeper upon the addition of ammonia water.
Million's reagent stains proteins a brick-red.
Concentrated solution of nickel sulphate colors proteins yellow
If sections are placed for an hour or two in a solution Buy Avapro Online of i Gm. of
sodium phospho-molybdate in 90 Gm. of distilled water and 5
Gm. of Buy Avapro Online nitric acid, the proteid substances appear as yellowish
The globulins (phytoglobulins) frequently occur in bodies called
go PHARMACEUTICAL BOTANY
Aleurone grains are small bodies found in seeds particularly those
containing oil, Buy Avapro Online and like starch grains often are characteristic of the
genus or species. Each aleurone grain consists of a ground sub-
stance (composed of amorphous proteid matter soluble in water,
dilute alkali or acid), in which are usually embedded one or more
phyto-globulins (insoluble in cold water, but soluble in less than i per
cent, solution of an alkali, in dilute HC1 and acetic acid), one or more
transparent globular globoids composed of Ca and Mg phosphate
PIG. 39. To show aleurone grains. A , Buy Avapro Online cells from cotyledon of seed of garden
bean; n, aleurone grains; m, starch; B, cells from endosperm of castor bean; a,
a, aleurone grain; I, ground substance; k, phytoglobulin; I, globoid. (A, After
Sachs; B, after Frank.)
(insoluble in water and dilute potash solution but soluble in i per
cent, acetic acid solution), and frequently a crystal of calcium
oxalate, the whole being enclosed by a protoplasmic membrane (so-
luble in water). (Fig. 39$.)
The proteins insoluble in the cell-sap water are made soluble Buy Avapro Online for
translocation by means of proteolytic enzymes which change them
into proteoses and peptones.
20. Mucilages and gums are those substances occurring in plants
which are soluble in water or swell in it, and which are precipitated
Mucilage is formed in plants in several ways, viz.; either as a
product of the protoplasm, as a disorganization product of some of
the carbohydrates, as a secondary thickening or addition to the cell
wall, or as a metamorphosis of it. In the first two cases the mucilage
is called cell-content mucilage; in the last two, membrane mucilage.
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