6 Field Museum of Natural History 



perennials while the cultivated cereals are, on the 

 whole, annuals. The ideal climate for wheat is one 

 with a mild winter, a cool and moist spring conducive 

 to abundant development of the vegetative part of the 

 plant, followed by a warm, dry summer for rapid 

 ripening of the grain. Wheats which in their proper 

 latitudes withstand the low temperature of winter 

 without injury are known as winter wheats. True 

 winter wheats are "winter annuals" only and will not 

 ripen seed when sown in the spring. They are sown 

 in the fall, and germinate and form roots before the 

 onset of cold weather. Starting in the spring with a 

 partly developed root system they make a vigorous, 

 early growth. They ordinarily show a higher yield, 

 are more likely to escape rust, and mature their grain 

 earlier than the spring sown wheats. The spring 

 wheats are more tender varieties that complete their 

 growth in one season and in spite of a later start 

 mature their grains. In northern latitudes only spring 

 wheats can be grown. In mild climates both spring 

 and winter wheats may be grown from fall sowing. 

 As a rule the hard winter wheats are more resistant 

 to cold than are the soft, but all wheats naturally be- 

 long to somewhat more moderate climates than their 

 northerly relative rye. 



Hard and soft wheats differ in the composition of 

 the grain. The soft wheats are richer in starch and 

 are likely to have large grains, while the hard, with 

 smaller grains, are relatively richer in gluten. Flour 

 made from soft wheat is esteemed for cake and pastry 

 making, but by itself is "weak" and out of a given 

 quantity does not make a large loaf. Hard wheats 

 make a "strong" flour which, on account of the binding 

 properties of gluten, retains the gas produced by the 

 yeast and make a light loaf. They are now generally 

 mixed in different proportions for various purposes. 



[22] 



