HYBRIDISATION AND WHEAT HYBRIDS 363 



In some wheats, two of the anthers are^hidden behind the overlapping edges 

 of the palea and require great care in their removal. Somewhat blunt-pointed 

 forceps are less liable to break the anthers than those with very fine points. 



6. Select an ear of the pollen parent, and with scissors cut off the upper half 

 of the glumes of a few of its median spikelets. With forceps remove any thus 

 exposed anthers which are bright yellow, and after pinching them dust the 

 escaping pollen on the styles of the emasculated flower ; leave the broken anther 

 in contact with the styles and allow the glumes to close. 



7. Enclose the crossed ear in an envelope of thin waterproof paper, and with 

 cotton tie the lower open end of the envelope round the upper part of the straw 

 so as to prevent the access of foreign pollen or insects . 



Where waterproof envelopes are not available, take a strip of thin soft paper 

 six inches wide and wind it three or four times round the crossed ear and upper 

 part of the straw ; tie above and below the ear to prevent foreign pollination. 



8. Label the crossed ear indicating the respective parents and date of the 

 cross. 



9. After a week examine the crossed ear, and if the stigmas are withered 

 remove the covering altogether. 



(If the stigmas are receptive, fresh pollen applied to them germinates im- 

 mediately and fertilisation is effected in forty-eight hours or less.) 



Raynbird, Shirreff, Pringle, and Vilmorin, among the earlier hybridists, 

 observed the extraordinary multiplicity of forms among the descendants 

 of hybrid wheats, but it is only since the re-discovery of Mendel's laws 

 of inheritance that any explanation has been given of the cause of the 

 diversity. 



In recent years there has been an accumulation of more or less pre- 

 cise knowledge of the mode of inheritance of the chief characters of the 

 species and races of wheat, which is summarised in the following pages. 

 In making clear some of the points which were previously obscure, the 

 Mendelian concepts of heritable factors and gametic purity have been 

 invaluable, but much remains to be discovered before all the facts of 

 inheritance in the highly complex hybridised wheat plant can be satis- 

 factorily explained. 



INHERITANCE OF THE CHIEF CHARACTERS OF THE WHEAT PLANT 



ERECT AND SPREADING HABIT (p. 69, Figs. 65, 66). Hybrids of 

 wheats with these characters are intermediate, the F 2 segregating in the 

 1:2:1 ratio. 



EARLY AND LATE RIPENING PERIOD. These characters are correlated 

 with the foregoing allelomorphic pair, early wheats always having upright 

 young shoots, while in the latest forms the young shoots are prostrate. 



Hybrids are intermediate with semi-erect young shoots (B, Fig. 66), 

 and segregate in F 2 in the 1:2:1 ratio. 



