VARIATION' 



317 



2. Environment conditions development of inherited characters.— 

 (a) Light and metabolism. In a general sense light conditions life 

 in all normally green plants. It certainly conditions normal develop- 

 ment 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 

 iniiorescense, but it is all done at the expense of the food storcrl up in 

 the bulbs. 



Fig. 55. — a, Typical wild pigeon, Scardafclla inca; b, the form dialcucos; r, 

 hraziliensis; d, ridgwayi; e, inca after three moultings in a moist atmosphere. 

 (After Beebe, from Babcock and Clausen.) 



b) Temperature and flower color. Baur reports an experiment with 

 a red variety of the Chinese primrose, Primula sinensis rubra. If 

 plants of this variety are raised by the usual method until about one 

 week before time to bloom and then some of the plants are put in a 

 warm room under partial shade (temperature from ^0° to 35° C.) and 

 the remainder in a cool house (temperature from 15° to 20° C), when 

 they bloom those in the warm temperature have pure white flowers 

 while those in the cool temperature have the normal red color of the 

 variety. Moreover, if plants are brought from the warm into the 



