428 THE WHEAT PLANT 



among the young plants and the deleterious effect which one plant has 

 upon another even of the same species when grown together. In Mont- 

 gomery's experiments the death-rate among wheat plants, grown in rows 

 8 inches apart and inch asunder in the row, was 23-38 per cent, the loss 

 being 12-25 P er cent amon g tne less crowded plants growing i| inches 

 asunder in the rows. 



The number of plants which survive until harvest under ordinary 

 field culture has rarely been determined, but the number of ripe ear- 

 bearing straws has been frequently counted, the number per acre ranging 

 from about 150 to 400 per square yard, where 2^-3 bushels of grain have 

 been sown. In many instances there are fewer straws with ears than 

 grains sown, owing to the high death-rate among the plants. 



It is found that a good crop is rarely obtained in this country where 

 the number of ears is less than about 300 per square yard. 



Not only is the number of ears per acre significant, but the number and 

 weight of the grains in each ear is of the greatest importance, and efforts 

 to increase the yield per acre are usually directed towards improvement in 

 this respect. 



The total yield of an ear is dependent upon the number of its spikelets 

 and the number of grains developed in each spikelet. 



The average number of spikelets in an ear of Bread Wheat (T. vulgar e) 

 is about 20, but it differs, though not very widely, in different varieties and 

 forms, some having an average of 18, others 22 or 23 per ear. 



In Rivet wheats (T. turgiduni) the average is higher, being about 25. 



The number of flowers in a spikelet varies from 3 to a possible 8 or 9, 

 but many of the upper flowers prove abortive, the number of grains which 

 develop varying from i to 7, the latter number being only met with in 

 the spikelets of ears borne upon plants which have been exceptionally 

 manured (Fig. 228). 



Well-grown ears of the field often bear 5 or 6 grains in each of the 3 

 or 4 median spikelets, the numbers falling gradually to i or 2 in the basal 

 and apical spikelets. 



Many of the spikelets at the base of smaller ears are abortive, the 

 number of these increasing with adverse climatic conditions, poverty of 

 the soil, and excessive tillering of plants sown earlier than September. 



The largest ears of an ordinary field crop in this country frequently 

 possess 40 to 50 grains, weighing from 1-8 to 2-25 grams, the smallest 

 not more than 12 or 14 grains, weighing '54--63 grams, an average ear 

 having from 25 to 30 grains, weighing 1-25 to 1-35 grams. 



In the following table are given the calculated yields per acre, when the 

 number of straws varies between 50 and 400, and the yield per ear between 

 5 gram (12 grains) and 3 grams (72 grains). 



