416 PHYSIOLOGY OF GROWTH. 



air is generally more favourable to the development of the stolons 

 than is dry air. 



We lay potatoes in moderately moist soil, so that they are com- 

 pletely covered by it. The large flower-pots containing the soil 

 are placed in a warm room under a zinc receiver. On germina- 

 tion the potatoes produce very long shoots with small leaves. 

 Furthermore many aerial roots develop, and soon stolons also, as 

 axillary shoots, which in the moist air bend downwards, and 

 frequently swell at their ends into small tubers. Frequently, 

 however, the tubers are unstalked and seated directly in the leaf 

 axils. The development of the plants under the conditions de- 

 scribed is not always exactly the same ; the variety of tuber is a 

 matter of importance in this connection. 2 Winter buds of Fagus, 

 according to recent researches, are said to burst only in the light. 

 My experiments on the subject are not yet completed. 



1 See Detmer, Pflanzenphysiologische Untersuchungen iiber Fermentbildung 

 und fermentative Processe, Jena, 1884, p. 34. In my experiments no water at 

 all was supplied to the potatoes. The water requisite for the growth of the 

 shoots streamed to their cells from the tissue of the tuber. 



2 For much detailed information see Vochting, Bibliotheca botanica, Cassel, 

 1887, Heft 4. 



