FORMATIVE INFLUENCE OF LIGHT 



145 



rich garden soil, and set upright in the center of each a large 

 sound potato of some " early " variety in such manner that the 

 upper end is exposed. Place in a 

 temperate room under diffuse light 

 and water sparingly. After a time the 

 germination of the tuber will produce 

 several stems from the different buds. 

 All of these should be destroyed ex- 

 cept one on each tuber. This will 

 develop a main axis, and stolons from 

 the basal part of the main axis. After 

 the stolons have attained a length 

 of 10 or 15 cm. the main axis is cut 

 away and one of the stolons is raised 

 and its end thrust into a small dark 

 chamber consisting of a zinc or card- 

 board box which may be tightly 

 closed. This box should be about 

 1 5 cm. by 1 1 cm. and one end should 

 be slit in such a manner that the FlG ?g shoot of Cam _ 



Stolon may be introduced sidewise, panula, showing rounded leaves 

 the slit closed with cotton wool to developed on upper lateral branch 



exclude light and then the lid put in ' ° e e ' 



place. It will be still better to have the box made of zinc and 

 the lid replaced by a slide. The box should exclude all light, 

 and should be shaded by cloth from the direct rays of the sun. 

 In order to receive the moisture accumulating in such enclosed 

 spaces containing transpiring shoots, a small vessel containing 

 sulphuric acid may be set inside the box. A stand or support 

 will serve to hold the box and other parts of the preparation in 

 place. The box should be opened from time to time to take 

 away the etiolated leaves which quickly turn yellow and die. 

 The formation of tubers may be soon noticed, and their growth 

 will be extensive inside of a month. 1 



1 Vochting, H. Ueber die Bilding der Knollen. Bibl. Bot. Hft. , 4. 1887. 



