92 PLANT LIFE ON THE FARM. 



effected by crossing the flowers of two separate species, 

 as in the case of the Alsike clover, which is said to be a 

 hybrid between the white or Dutch clover and the red 

 clover. 



Chemical Changes. The chemical changes which occur 

 during the formation of the flower, and especially during 

 the ripening of the seed, have already been alluded to. 

 The contrast between the composition of the leaves and that 

 of the pollen and of the seeds is very striking, and analysis 

 brings out the fact of the accumulation of nitrogenous and 

 phosphatic and mineral matters in the pollen and in the seed. 

 In haymaking it is better, if possible, to mow before the 

 leaves are exhausted of their contents by the seeds, or at 

 any rate, before the latter are shed. If cutting be delayed, 

 a great part of the nutritive matter is withdrawn from the 

 leaves and stems to be stored up in the seeds, which fall 

 readily when ripe, and thus occasion a loss to the farmer. 

 Again, as it has been shown that the seeds of cereals 

 contain their full proportion of nutritive matter some little 

 time before they would be considered thoroughly ripe, early 

 cutting, where practicable, is to be recommended to secure 

 the crop and obviate possible loss from delay. 



