630 FARM ' SEEDS : GENERAL 



seeds with waxy or hairy surfaces, or those with loose husks 

 round them, as sainfoin and grasses, it is a useless and mislead- 

 ing method. 



{b) 'Absolute Weight.' — By this is meant the weight of a 

 certain number of seeds, usually 100 or 1000; from it the 

 average weight of a single seed of the sample can be calculated. 

 It is found that so long as we compare the same kind of seeds, 

 the absolute weight is directly proportional to their size, except 

 in the case of abnormally large or very small ones. By weighing 

 say 100 grains of barley from two different samples, we caii 

 readily determine which is the larger in size of grain. 



It is well known that the size of seeds is not the same for all 

 plants. Usually those which produce a small number of seeds 

 from one flower, as the pea and bean, have larger seeds than 

 those which give rise to many, as the poppy. Seeds of the 

 same species of plant are however not always of uniform size, 

 variation often occurring even in the same pod or ear. 



Alterations in size are often associated with differences in the 

 position of the seed or fruit upon the plant. In the ears of 

 wheat, barley and rye, the heaviest grains are met with in the 

 spikelets, at a point about half way from the base of the ear, 

 sometimes a little below this point or a little above it according 

 to the variety of wheat or barley examined. Not only do the 

 grains increase in weight from the base to the middle of the eai 

 and then decrease to the tip, but a similar relation in size to 

 position on the inflorescence is seen on examining the spikelets, 

 the second flower in each nearly always producing the heaviest 

 grain. 



In the Leguminosae, peas and beans, the largest seeds are found 

 near the middle of the pods and not at the ends. Besides the 

 position of the seed on the plant influencing its size and therefore 

 its weight, climatic conditions and manures are concerned in 

 modifying the size of seeds. Although in all cases it is not 

 possible in our present state of knowledge to explain the causes 



