368 Plant Physiology 



it may serve as a valuable control suggestion in hybridi- 

 zation work. 



216. False xenia. - - Certain beans and peas show ex- 

 ternally in the color of the embryo the immediate effects 

 of the pollen. The seed-coats are more or less colorless, 

 and the characteristics of the embryo are, therefore, ap- 

 parent. Physiologically this is in no way comparable to 

 the previous phenomenon, and if the term " xenia ' is 

 used in this connection, it should be expressed false xenia. 



217. Other secondary effects of pollination. - - Under 

 xenia we have considered only those instances of the sub- 

 sidiary effects of the pollen which may be attributed 

 directly to fertilization, or double fertilization, and 

 manifest through effects produced in a readily explained 

 manner upon the embryo and endosperm. A certain 

 special stimulating action of pollination upon structures 

 outside of the ovule was long ago suggested by Focke and 

 others. The problem may, for the moment, be restricted 

 to cases in which there is fertilization. The question may 

 then be formulated as follows : In the normal production 

 of fertile seeds, is there any evidence that pollen from 

 different varieties or species will influence the form, color, 

 or quality of the fruit? 



Beyond all question, the form of the fruit, and even the 

 quality of the fruit, will be affected when only a few ovules 

 are fertilized; for the reason that there will be incomplete 

 development of the fruit as a whole in the great majority 

 of plants, notably in many varieties of the tomato and 

 apple. Opinions differ regarding the important effect of 

 pollen from different varieties on the form or color of fruit 

 when fertilization is complete. In various horticultural 



