250 The Plant World. 



sively and were found to be a convenient and very valuable 

 means of investigation. 



The young potato plants were procured by sprouting the 

 tubers on a perforated gutta-percha disk, similar to the par- 

 affined galvanized iron wire netting used by Livingston for 

 germinating wheat. * The gutta-percha was closely per- 

 forated by means of a drill. It has a hard, stiff surface, 

 floats level upon the water, and does not permit any sagging 

 as do perforated cork sheets and the iron wire netting. The 

 disk was floated upon corks fixed to its edge so that it was 

 held just at the surface of the water in a granite iron pan. 

 If allowed to become submerged the potatoes quickly decay. 



Figure lo shows the method of starting growth. The 

 disk, as shown in the cut, is supported by an iron stand, in 

 order to show the corks and roots. The water in the pan is 

 two to three inches in depth. It must be changed daily. 

 The tubers are cut in small pieces, so that each will include 

 an eye, and placed on the floating disk. Sprouting takes place 

 and definite growth begins within about a week. The roots 

 pass through the holes of the float into the liquid. If good 

 tubers are used the growth is uniform and a large number 

 of plants of the same size can be secured from a single pan. 

 When the plant is about two inches high the potato is re- 

 moved from the germination apparatus to be used in the 

 water culture test. The young plant with its roots is cut 

 from the mother potato so as to leave no part of the tuber 

 with It. 



Figure lo (below) shows the material necessary in using 

 the potato plant in water culture experiments. The corks used 

 as stoppers are one-half inch in thickness. A vertical wedge 

 Is removed, which is truncated at its inner angle, so it can be 

 replaced in position when the seedling is placed in the groove 



♦ The Plant World, 9-1-1906. 



