342 HOW CROPS GROW. 



wheat and barley produce the heaviest kernels. Nobbe 

 numbered and weighed the spikelets from an ear of six- 

 rowed barley and from one of winter wheat. Either ear 

 contained 27 spikelets, each with three kernels. The 

 kernels of the smallest barley-spikelet, No. 2, from the 

 base of the ear, weighed 1.5 milligrams ; those of the 

 largest, No. 10, weighed 103.5 mg. No. 27 weighed 

 32.5 mg. The corresponding numbers in wheat weighed 

 0.5, 34.5 and .10.8 mg. 



In case of barley, each of the first five spikelets, .count- 

 ing from the base, weighed less than 70 milligrams. 

 The 6th to the 22d, inclusive, weighed 75 mg. or more. 

 The 7th to the 16th weighed 90 mg. or more. The 17th 

 to the 21st, 80 mg. or more. Thence, to the tip, the 

 weight rapidly declined to about 30 milligrams. 



The wheat kernels exhibited quite similar variation of 

 weight. 



Dividing the 27 spikelets into three groups of nine 

 each, we have the following comparison of weights of 

 seeds, to which is added the total lengths of the rootlets 

 that were formed after germination had gone on for five 

 days : 



BARLEY. WHEAT. 



Weight. Length of Root. Weight. Length of Root. 

 Spikelets, 1 to 9 426 mg. 670mm. 153 mg. 223 mm. 



10 to 18 828 3281 " 282 1094 



18 to 27 512 1364 191 " 454 



The seeds of the middle portion of the ears of barley and 

 wheat are thus seen to be very considerably heavier than 

 those of cither the base or tip, and also show greater ger- 

 minative vigor, as measured by the comparative growth 

 of the roots in a given short time. 



The greater weight and germinative energy of the 

 seeds from the middle of the cars, stand in relation to 

 the fact that these seeds are the oldest the flowers from 

 which thev develop being the first to open and fructify. 

 In case of a head of summer rye, Nobbe found that the 



