15 



made to blossom by this means, and new varieties have 

 been obtained by crossing from them. When enter- 

 taining the idea of crossing varieties it is obviously 

 necessary to regulate the time of planting so that the 

 plants of varieties which, under ordinary circumstances, 

 do not produce flowers at the same time, may be made 

 to do so simultaneously, otherwise a year may be lost. 



It is found that flowers of one plant do not fertilise 

 other flowers on the same plant, while the pollen from 

 another plant does so very readily. In fact, the ferti- 

 lisation is too readily effected, as the experimenter 

 experiences great trouble in keeping alien plants from 

 affecting those with which he is treating. The potato 

 is one of those plants which is fertilised without the 

 aid of insects. The fine pollen dust is readily trans- 

 ported by wind, and so susceptible is the plant 

 that the seeds from one plant are frequently found to 

 produce potatoes of many varying types. When 

 systematic hybridisation is carried out it is necessary 

 that the plants employed should be kept perfectly 

 isolated, or true crossing will in all probability be 

 interfered with. Most hybridisers prefer growing them 

 in houses where they are under easy control ; but at 

 any rate, from the time that the buds begin to show 

 signs of opening the plants should be placed under 

 glass shades. When the flow.ers are developed the 

 shades should be opened just sufficiently to permit the 

 hand to be inserted. The blossoms gathered should 

 be covered before being withdrawn from the shade, 

 and it is best to open the shade on the side opposite to 



