IN THE TROPICS : ITT. 97 



ACCOUNT OF CORRENS' EXPERIMENTS ON 



XENIA." 



Any one who sets about describing experiments in the cross 

 breeding of Indian corn must of necessity begin with a 

 reference to the admirable work of Correns described in his 

 monograph in Bibliotheka Botanika, 1901. Correns has 

 there analysed the behaviour on crossing of a large number of 

 characters, especially those characters of the grain which may be 

 affected as the immediate result of the cross, owing to so 

 called " xenia."* resulting from the double fertilization which 

 takes place in maize. The following brief summary may serve 

 to call to mind a few of the more important details of Correns 's 

 work. His more general conclusions have already been short- 

 ly referred to. 



Correns found that characters belonging to the following 

 categories followed Mendel's law on crossing; i.e., were 

 schizogonous : — 



1. Colour of the pericarp. (Not fully proved.) 



2. Colour of the endosperm. (Yellow, or non-yellow — 



i.e., '" white.") 

 :). Colour of the aleurone layer. (Blue, or non-blue — 

 i.e., -'white.") 



4. Chemical nature of the endosperm. (Starchy, or 



sugary.) 



5. Shape of the aleurone cells. (Long or short.) 

 The following pairs of characters on the other hand are stated 



by Correns to be homoogonous ; i.e., the cross-bred plants 

 produce gametes bearing these characters unsegregated : — 



1. Shape of grain. (Round or pointed.) 



2. Size of grains. 



3. Relative weight of embryo and endosperm. 



* The term xenia would probably be better confined to cases of 

 direct action by the embryo upon the maternal tissues, but since 

 there is no good term which can be used to denote the phenomena in 

 maize, I have retained the word " xenia," placing it between inverted 



commas to indicate its special application. 



