CITRUS CULTURE IN CALIFORNIA POLLINATION. 35 



and its supremacy destroyed. When that was accomplished, 

 those qualities that nature used to protect the seed were either 

 without necessity or modified to the changed habits of the new 

 tree. As these changes were produced, the whole tree was 

 acted upon to adjust a correlated growth. The germ cells were 

 changed in their capacity to produce a constant type. The 

 vegetative functions were immediately increased, and those 

 parts of the tree impulse -put forth a growth modifying those 

 protective growths built upon the defense and perpetuity of the 

 seed. As an immediate result of the loss in the pollen impulse, 

 the leaf increased in surface. The root cells were enlarged 

 and enabled to absorb liquids to meet an increase of leaf 

 evaporation. The whole tree acquired a greater heat range 

 and became more tropical. These modifications of the micro- 

 scopic pollen cell in its constructive energy to maintain a per- 

 manent type are seen in the habits of growth and fruit of the 

 sweet orange (Citrus aurantiuvi) of our orchards. 



Citrus Aurantium. — This orange is in such marked contrast 

 to the bitter orange that eminent authorities have debated 

 its origin, and have considered it a species equal with the 

 bitter orange, and awarded to both the ancestry of whole 

 groups of varieties. It carries a strong though weakened 

 reproductive function. Its departure from the type of the 

 bitter orange is in the loss of staminal power. The pistillate 

 or vegetable growths have increased by a readjustment of plant 

 energy in the floral branch which has weakened the virility of 

 the pollen impulse. 



When the two varieties are compared, the necessity for a 

 different parentage does not appear. The lines of modifica- 

 tion follow the generative impulse, and this possibility of the 

 germ type to variation gives the key to unlock the cause of 

 seed and bud variation in the great number of varieties and 

 monstrosities. The generative force broken in the type unit, 

 the combinations of its qualities were resolved into groups. 

 The type unit being impossible, the group unit appears in the 

 pollen, the seed, and the bud, giving us the varieties of the 

 orchard, each having one or more characteristics of the 

 historic type. 



The sweet orange is intermediate between the bitter orange 

 and the seedless varieties. In comparison with the bitter 



