270 PLANT AND ORGANIC CHEMISTRY 
pared will be found in this respect distinct. The gradual change 
from the bright greens of the early spring foliage to the duller 
greens of late summer illustrates the transmutation of color 
which may be observed in plants, and I would suggest that this 
same gradation may be seen on the large evolutionary planes 
of all plant groups, chlorophyll, like the plants, being at differ¬ 
ent evolutionary stages; for example, in many Algae and lower 
plants it appears as light bright greens, and finally in the darker 
greens of the higher plants. 
Considering in general the chemical compounds of flower¬ 
ing plants among the apetals and monocotyledons on the first 
evolutionary plane, where the plant elements are simple, tan¬ 
nin, wax, starch, aromatic or acrid principles, and the oils and 
sugar of the palm are the most conspicuous substances. These 
compounds are found in the same or in neighboring plants, 
and their association is doubtless of evolutionary significance. 
Glucosides or alkaloids, though occurring in some few of these 
plants, are not characteristic of this stage of evolution. 
Tannin is a general name for a class of substances which 
presents many aspects in different plants. It first appears, as 
was stated, in the liverworts, combined with large quantities 
of starch and wax; then in ferns. Among the amental apetal- 
ous groups it is one of the conspicuous compounds, also asso¬ 
ciated with starch; the casuarina, willow, poplar, hazel, oak, 
beech, chestnut, alder, and birch containing large quantities. 
Tannin is widely distributed, though especially in the leaves, 
barks, 1 seeds, and rinds of fruits, and in other plants in con¬ 
siderable quantities, as the maple, sumach, tea, in many ber¬ 
ries, the holly, and the seeds and stalks of the grape-vine. 
Tormentilla erecta , 2 Rosaceae, yields from six to twenty per 
cent, tannin, and, although this compound is present in mono- 
and di-cotyledonous plants, it seems to be more prominent in 
the apetalous on the first evolutionary plane, and to occur less, 
if at all, in the highest plants. When it is remembered that 
tannin is found in greater abundance in lower plants, which I 
1 “Repartition du Tannin dans les Diverses Regions du Bois de Chene,” 
Ann. de la Science Agr. 
2 Fraas, Ergebnisse , Landw. Versuche , München, 1861. 
