70 DISEASE IN PLANTS. 



SO forth ; but I am convinced that the agri- 

 culturist of the future and the same applies to 

 the horticulturist, planter and forester will have 

 to concern himself more systematically with the 

 working and the variability of the plant, and par- 

 ticularly with what Darwin termed Variation under 

 Domestication, than has always been the custom 

 in the past. The subject of the plasticity of culti- 

 vated plants, and especially of hybrids, is in one 

 sense an old one ; but much work is being done 

 which proves, as such work is apt to do, that very 

 much more may be done by well-planned experi- 

 ments on the selection of new varieties raised by 

 hybridising and cultivation. 



In illustration of this point, a short summary 

 of some of the results of crossing different species 

 of wheat, barley, oats, peas, beet, etc., may serve 

 to show what has been gained and what may be 

 hoped for in these directions. It should be stat-ed 

 that much has been done and is being done in 

 this country as well as abroad, as witness English 

 varieties of corn, peas, and potatoes, and the 

 recent experiments on crossing various kinds of 

 maize in America. 



The hybridiser grows his cereals, etc., in pots 

 until ready for crossing, and then takes them into 

 the laboratory, removes the weaker spikelets, and 

 takes out the young stamens from the flowers left 

 on the plant. The female plant is then ready, and 

 the flowers covered with paper caps. The pollen, 

 obtained by a clean wet brush from the plant 

 chosen as the father, is then carefully placed in 



