HIGHER AND LOWER PLANTS 271 



have 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 lalifolia (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 Heckel's 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. 



