THE PLANT 



27 



jectures as to the utility of the lint to the plant for ab- 

 sorbing and retaining water instead of acting as seed- 

 wings. Cotton-seed germinates best when 

 Water and j in water? half covered . jf laid on we t 

 Germination. * 



blotting-paper in the conventional way tor 



making tests of germination with many other seeds, very 



C 



FIG. 3. THE ACTION OF LIMITING FACTORS. (VERY DIAGRAMMATIC.) 



Three varying factors are indicated above (A, B, and 6') as curves. Below 

 is represented the behaviour of a plant under their influence, as first one 

 and then another becomes " limiting." 



If A represented the temperature, B the water-content, of the soil, and 

 C the size of the living root-system (as affected by the water-table), 

 this diagram would roughly portray the life-history of an Egyptian 

 cotton-field. 



few of the seeds germinate, whatever the temperature, 

 the seed-coat being unable to absorb enough water.* 



* The cuticle of the seed-coat is slightly waxy, probably 

 from the same wax which has long been known to occur on the 

 lint. Until this wax has been broken by the initial swelling of 

 the seed, the absorption of water is difficult. 



