183 



a most laborious proccess, for in 1822 he states * that the potatoes, 

 being " shoots, or branches, which have grown thick instead of 

 elongating," gardeners should take pains to plant the tubers right 

 side up with care, as they " retain the disposition of branches to 

 propel their sap to their leading buds, or points most distant 

 from the stems of the plants, of which they once formed parts." 



In this same paper he describes another experiment, in which 

 he planted seed tubers above the soil so that only the fibrous 

 roots growing from them entered the ground. Then, by remov- 

 ing all blossoms and runners that appeared, he secured " a nu- 

 merous crop of young tubers," growing sessile at the buds or 

 " eyes " of the old. 



Moretti t describes a modification of one of the experiments 

 performed by Knight in 1806. By cutting a potato stem near 

 its base so that the upper portion is joined to the root end only 

 by means of a small strip, nourishment was prevented from being 

 translocated to the tuberiferous stolons. Under this condition 

 tubers formed in the leaf axils along the branches exposed to 

 light. 



In more recent years de Vries is said by Vochting to have 

 secured the formation of tubers by Solaiunn ticberoswn in the light, 

 but the original paper % has not been accessible to the writer. 



The most recent and most extensive experiments on tuberiza- 

 tion are by Vochting. § He did not succeed in securing the 

 formation of tubers in the light in all varieties, but in the variety 

 " Saucisse," while the main stem never developed tubers in the 

 light, its side branches may become transformed into tubers 

 under such conditions. In his later experiments Vochting || 



* Knight. An account of an improved method of raising early potatoes in the 

 open ground. Trans. Hort. Soc. London, 4: 447. 1822. 



t DeCandoUe, A. P. Pflanzen-physiologie. Stuttgart und Tubingen, 1833. De- 

 Candolle quotes Moretti et Guieciardi, De nonnullis physiologico-botanicis animad- 

 versionibus. 1831. 



X DeVries, H. Beitrage zur speciellen Physiologie landwirtschafllicher Kultur- 

 ptlanzen. Landwirth. Jahrb. 7 : ig, 217, 591, 659. 1878. 



^ Vochting. Ueber die Bildung der Knollen. Bibliotheca Botanica, i*. 1887 ; 

 Zur Physiologie der Knollengewachse. Leipzig, 1899. Also in Jahrb. Wiss. Bor. 

 34 : 108. 1900 ; Ueber die Keimung der Kartoffelknollen. Bot. Zeit. 5 : 87. 1902. 



II /. c. 1902. 



