Vol.6 



No. 9 



TORREYA 



September, igo6 



TUBER-FORMATION IN SOLANUM TUBEROSUM IN 



DAYLIGHT 



By C. Stuart Gager 



Thomas Andrew Knight, writing in 1829 to Dr. Bevan, said :* 

 " I have been and am still engaged in some experiments on the 

 potato, which plant has given me more physiological information 

 than all the remainder of the vegetable world ; and where it has 

 not given me the information I wanted, it has directed me where 

 to find it." 



It is too well known to need statement here, that the potato 

 tuber is a branch, modified as an organ for the storage of food, 

 and resulting from the thickening of stolons that arise from the 

 basal parts of the main axis. This homology was recognized by 

 Knight as early as 1801, and was later demonstrated by Turpin | 

 in 1828. 



By an ingenious contrivance. Knight J, in 1806, succeeded in 

 growing potato plants so that only the fibrous roots penetrated 

 the soil. By preventing the formation of tubers on the stolons 

 that normally would have developed underground, and also on 

 the lateral branches of the aerial portion of the shoot, he suc- 

 ceeded in getting the plants to form tubers at " the extremities of 

 the branches, those being the points most distant from the earth, 



*A selection of the physiological and horticultural papers of T. A. Knight, p. 63, 

 London, I 841. 



f Turpin, J. F. Memoire sur 1' organisation interieure et exterieure des tubercules 

 du Solanum tuberosum et de I'Helianthus tuberosus, consideree comme une veritable 

 tige souterraine, et sur ces tiges. Memoires du Museum d' Histoire Naturelle. Read 

 Dec. 27, 1828. 



J Knight, T. A. On the inverted action of the alburnous vessels of trees. Phil. 

 Trans. 96 : 293. 1806. 



[No. 8, Vol. 6, of TORREYA, comprising pages 157-180, was issued August 25, 

 1906.] 



181 



