362 THE WHEAT PLANT 



age of the pollen, the temperature and moisture of the atmosphere at the 

 time of pollination, and the time of day at which the operation is per- 

 formed, all have an influence upon the result. 



While pollinations may be effective at all times of the day, I have had 

 the best returns from those made in the morning before 10 A.M. At that 

 time the tendency to rapid drying of the temporarily exposed parts of the 

 flower is much less than during the hotter part of the day. 



The hybrid grains are frequently smaller and more shrivelled than 

 self- fertilised grains of the same ear, more especially when the two parents 

 belong to different races, and small imperfectly formed grain sometimes 

 results after cross-fertilisation between two nearly related forms, although 

 plump grains are equally frequent. 



The embryos of shrivelled hybrid grains are usually delicate, and 

 special care is required in rearing them. It is best to sow the grain in 

 pots under glass rather than in the open soil, where the risk of destruction 

 of the young plants by frosts, rain, and pests is greater. 



The shrivelled endosperm of hybrid grains is probably connected 

 with the fact that, like the embryo, it is of hybrid origin, or possibly its 

 feeble development is attributable to the failure of the second male gamete 

 to unite with the fusion-nucleus of the embryo sac. 



The method of the artificial hybridisation of wheat is simple, never- 

 theless there are certain important points of detail to which it is useful to 

 direct attention. 



Since anthesis commences usually in two to five days after the escape 

 of the ear from the upper leaf-sheath, crossing must be undertaken during 

 that period or the chances of finding flowers in which the anthers have 

 not already shed their pollen on the adjacent stigmas will be small. 



After selecting the grain-bearing female parent, the following is the 

 plan of operations which I adopt : 



1 . Cut off the upper third of the ear with fine pointed scissors and pull off 

 completely four or five of the lowest spikelets. 



2. Of the remaining spikelets remove completely every alternate one on both 

 sides of the rachis. 



3. Take hold of the tips of the few spikelets left and pull outwards and down- 

 wards ; this removes the upper florets of the spikelets, and leaves for crossing 

 only the two lowest and largest florets of each. 



4. Gently press the glumes of the florets to be emasculated, and insert the 

 point of a pair of closed forceps between the upper edges of the glume and palea. 

 On releasing the forceps the glumes are separated and the anthers are exposed 

 to view. 



5. If the anthers are green and erect they can often all be removed together, 

 but if further advanced in their development they should be removed singly, 

 care being taken not to burst them in the process. 



