SEED-SOWING. 33 



soluble arseniates prevented germination altogether by destroy- 

 ing the germ or embryo. 



Heat assists germination by quickening the action of the 

 tissues; and darkness is favourable to the liberation of the 

 carbon and the formation of carbonic acid gas, a process 

 which takes place in the growth of all seeds. The relative 

 length of time in which seeds germinate is very variable ; some, 

 as Mustard, Cress, and Radishes, for example, appearing above 

 the earth a few hours after they are sown, while other seeds lie 

 in the ground for years. Seeds of many hardy trees and 

 shrubs, as Conifers, Hawthorn, &c., germinate the first or 

 second year ; while, if the ground is left undisturbed, straggling 

 seedlings make their appearance for years afterwards. Some 

 seeds will germinate after having been kept above ground for 

 many years, while others fail to grow the second year, and the 

 fact is as unaccountable as it is true. Seeds buried deep in 

 the earth that is, below the effects of air and external tem- 

 perature retain their vegetating power for lengthened periods, 

 and spring into life again when brought near the surface, so as 

 to be influenced by heat and air. Evidence of this is afforded 

 by the deep cuttings made for bridges and railways in nearly 

 all parts of the country ; and it will be found that the botany 

 of railway embankments is often far richer than the adjoining 

 country. 



The quality and size of seeds, as pointed out many years ago 

 by Mr T. A. Knight, demand some attention, since on these 

 points the success or failure of a crop in a great measure 

 depends. Dr Gustav Marck has recently published a valu- 

 able paper on this important subject, embodying the results 

 of a great number of experiments made by him at the experi- 

 mental stations at Halle and Leipsic. Most convincing proof 

 of the superior value of large seed is furnished by the results 

 of some of his experiments in the garden. Beans and Peas 

 were planted in the garden, small and large seeds of each 

 kind being planted on adjacent plots, the Beans 12 inches 

 apart each way, and the Peas in rows 10 inches apart and 2 

 inches asunder in the row. The crop was carefully harvested, 

 and measured when ripe, and the progress of growth was closely 

 watched during the season. The larger and more uniform 

 growth of the plants from the larger seeds, from the beginning 

 to the end of the season, is shown in the condensed tabular 

 form in which we have arranged the results of these experi- 

 ments. Height is given in inches, and weight in ounces, if 

 not otherwise specified. 



