180 PEEMANEiNT N0ESEEIE3. 



few inches length of the ridge flanking the distributing channel. 

 When the beds are sufficiently flooded, the ridge is restored, the 

 dam placed across the feed channel having been previously re- 

 moved. It would be a great improvement, and one easily effected, 

 to maintain a permanent opening in the ridge of earth, and to fit 

 iiito it a moveable dam formed of a piece of wood, flat stone, hard 

 earthenware or sheet iron. Similar dams should be used also in 

 the feed channel. In every other respect the arrangement of beds, 

 paths and channels would be the same as in the percolation system. 



ARTICLE 8. 



Prepaeation and management of seed-beds. 



Before proceeding to describe the actual preparation and 

 management of the seed-beds, it is necessary to say a few words 

 regarding the process of germination and the methods of forcing 

 it, and the time for sowing the seeds. 



§ 1. — Germination and methods of forcing it. 



In the germination of all seeds three distinct stages may be 

 recognised : — 



(i) The Imbibition of Water. — First of all the germ and also 

 the perisperm, if there is any, absorb water and swell up. 

 The highar, within certain limits, the temperature is, the more 

 rapidly does this process take place. The covering of the seed 

 may also absorb water and bcecome more soft and yielding. 



(ii) Chemical Changes of State of the Reserve Ma- 

 terials. — Under the influence of heat, within certain limits, and 

 the special ferments present in the seed, the water-gorged reserve 

 materials absorb oxygen from the air, and from generally inso- 

 luble substances incapable of directly forming plant tissues, . be- 

 come converted into soluble substances capable of at once becom- 

 ing living tissue. 



(iii) Development of the Embryo. — By means of the newly 

 formed substances, under the continued influence of 'moisture, 

 heat and oxygen, new cells are formed in the embryo, which thus 

 increases rapidly in size, breaks through the enclosing shell and 

 develops into a perfect plant. This stage begins before the com- 

 pletion of the second, and much of it is contemporaneous with it. 



It is evident that the first stage can be entirely, the second 

 stage partially, completed before the seeds are sown, thus dimi- 

 nishing the time during which they will have to lie in the soil 



