VARIATION 25 
(d) Moisture and Plumage Color.—Beebe experimented with the pigeon, 
Scardafella inca. This species, as found in North and Central America, 
is very constant in color of plumage, but in the moist tropics the following 
darker colored forms occur: in Honduras, dialewcos; in Venezuela, ridqwayt; 
in Brazil, braziliensis; and these differ in the amount of pigment in the 
feathers. By subjecting birds of the northern type to an especially 
moist atmosphere, Beebe caused them to be so influenced that with each 
new moulting, whether natural or artificially induced, they always de- 
veloped darker feathers. Thus a wild bird having pigment in 25.9 per 
cent. of its area, would have after the second moulting under experimental 
conditions, 38 per cent. and after the third, 41.6 per cent. Thus during 
the experiment the typical form assumed the appearance of the three other 
forms and finally developed plumage markings which have never been 
seen in nature. Fig. 8 shows the type form, znca, the three geographical 
variants, and the darkest artificially produced form, 
Fie. 9.—Plants of Scilla, started alike but the pot on the right was kept in a dark room. 
(From Ganong.) 
2. Environment Conditions Development of Inherited Characters.— 
(a) Light and Metabolism.—tIn a general sense light conditions life in all 
normally green plants. It certainly conditions normal development in 
such plants. Potatoes sprouted in a dark room develop no chlorophyll 
in the stems and the rudimentary leaves are abortive. In many bulbous 
plants, however, the influence of moisture and heat are sufficient to 
induce leaf growth and even development of the inflorescence, but. it 
is all done at the expense of the food stored up in the bulb as is shown 
in Fig. 9. 
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