late sowings. In the first place, the percentage of germination was lower; 

 in the second place, the grain from late sown and late harvested seed also 

 required a longer time for germination. From Haberlandt's earlier investi- 

 gations in this line, showing a lesser development of grain in bulk as well 

 as in absolute and specific weight, it is further seen that the amount of soil 

 moisture alone is not the only cause of the difference between late and early 

 sowing. In these experiments the plants had a sufficient water supply, from 

 the beginning, and yet showed these different proportions. 



Thiel's experiments with late sowings were made at various times in the 

 autumn. The time of harvesting for all the plants, even of widely different 

 periods of sowing, was approximately the same, but very late sown seed 

 had a very small yield so far as it remained alive at all. Indeed Thiel rightly 

 calls attention here to the fact that late sown seed sprouted simultaneously 

 with that sown earlier with corresponding spring weather, without, however, 

 having had time to collect sufficient material for an abundant development 

 as did the plants grown from seed sown earlier. Naturally the constitution 

 of the seed plays a considerable role here. The older the seed, the more 

 slowly the reserve substances are mobilized. With ripening and subsequent 

 maturing, the amounts of sugar and amido nitrogen compounds decrease^ 

 and do not become prominent again until germination. The more or less 

 favorable sprouting of the seed depends on its age and the soil constitution. 

 At this point we will insert the warning that no reliance should be placed on 

 the results of other germinative tests, but one's own soil must be tested di- 

 rectly as to its behavior with different seeds. Seed which keeps well, accord- 

 ing to common germinating tests, may give poor results, especially in heavy 

 soils and, conversely, a light soil may often help seed to make a good growth, 

 which developed only a moderate quality in the germinating bed. Hiltner's" 

 report, for example, on newly harvested rye, which had suffered from a 

 thunder storm, showed that it grew well in some fields, but absolutely would 

 not grow in heavy soil. In another case, rye, developing 97 per cent, seed- 

 lings in a germinating test, molded almost entirely on one field, while in an 

 adjacent one it gave normal growth. 



Souring of Seed. 



In the section on too deep sowing (p. 106) we have already considered 

 the disadvantages to which seed is often exposed in heavy or in incrusted soils 

 with a large water content. Even germinated seed has to struggle against 

 difficulties due to physical constitution of the soil; viz., from an excess of 

 water in heavy soils. Here is found also souring of seed, which, to be sure, 

 can occur also in light soils, but has been observed usually only in heavy, 

 tough soils. 



The souring is due to a decay of the roots which have been longer 

 in contact with standing water, charged with organic substances. Most roots 



1 Johannsen, W., Studier over Planternes periodiske Livs yttringer, I; cit. Bot. 

 Jahresb. 1897, I, p. 143. 



2 Hiltner, L., in Prakt. Blatter f. Pflanzenbau u. Pflanzenchutz, 1903, Part I. 



