HIGHER AND LOWER PLANTS 
271 
h^ve compared as formative to the formed or higher evolution¬ 
ary groups, it is a still further illustration of what was stated 
about the higher percentage of ash-constituents in lower plants. 
Physiologists differ as to the tannin functions in plants. It 
probably serves several purposes; according to Schell, as a 
plastic material for the building up of tissues, especially where 
starch or fats are absent; or it exists as a subordinate product. 
It is certainly true that some tannins play a distinct role as the 
source of many vegetable colors,—the reds and blues of flowers, 
the brown of tree-barks, and the colors of changing leaves owing 
their origin to this source. 
The large quantity of starch in most tannin plants is remark¬ 
able; and Sachs believes it, or a fixed oil, to be the mother-sub¬ 
stance of tannin. 
Datiscin, 1 a kind of starch, is found in the Datisca order, 
and, among the monocotyledons, the palms occur on the same 
plane, and in most of their genera contain large quantities of 
starch, eight hundred pounds of sago having been obtained from 
one plant of Metroxylon, or the sago-palm species. The Arum 
pandanus (screw-pine) and bulrush orders yield much starch; 
of the latter plants, 12.5 per cent from Typha latijolia (Lecoq). 
Large quantities of wax are found in species of the myrtle, 
and also of the palm. 
On the second plane, or multiplicity of floral parts, the chem¬ 
ical constituents become much more numerous at this stage. 
Under the apetalous and monocotyledonous groups, volatile, 
pungent, and aromatic principles, alkaloids, sugars, coloring- 
matters, camphors, resins, starch, and glucosides appear promi¬ 
nently. The lower dicotyledonous plants reproduce many of 
the compounds of the other two classes, for the Rosaceae con¬ 
tain the tannins of the lower apetalous plants and parallel 
groups, and the glucosides of the higher monocotyledons. 
Cane sugar is a prominent compound here. If a horizontal 
line be drawn from a given point of HeckeFs scheme it passes 
through the apetalous, mono- and di-cotyledonous groups, which 
contain this substance most abundantly, — namely, the sugar 
1 According to Stenhouse, datiscin is a crystalline glucosidal bitter sub¬ 
stance. 
