132 



gone an especially strong' development, or had becopie fitted to 

 replace the lost peripheral phloenj bundle s-*-. 

 « 

 The observations of deVries and Vochting furnish valuable 

 conclusions. BeVries (loc. cit.) describes a peculiarly abnor- 

 mal potato tuber, from v^hich three well-leaved sprouts were pro- 

 duced, which, however, lacked stolons. Two other eyes of the 

 mother tuber, hov^ever, produced stolons without the requisite 

 leaf-shoots. "The nutritive substances formed in the leaves did' 

 not find on the bark of the stalk the usual place of deposition, 

 and were used successfully only in those tubers which bore sto- 

 (145) Ions. Apparently for this purpose they had to transverse the 



old tuber". The vessels here rartde use of had undergone a strik- 

 ingly vigorous development :-T "b;it had not attained to the forma- 

 tion of a continuous woody-layer, although several bundles had 

 united into groups. Bach single bundle, however, had been devel- 

 oped to a degree not otherwise attained in potatoes, — Bhe wood 

 consisted' of wood-fibres and d\zcts arranged in rows, which usu- 

 ally showed a very distinct reticulated wgll-forRBtion. The 

 phloem bundles showed a corresponding development, but did not 

 noticeably differ in structure from th& primary phloem". This 

 description by deVries does not decide the question whether an 

 activity-hyperplasia is actually present in the h^rperplagtic 

 vascular bundles which he observed, or not; i. e., whether in- 

 creased demand has caused the abnormal development -of the vas-^ 

 oular tissues, or whether probably some other reasons,, unknown 

 to us, have paused the abundant formation of their vascular 

 bundles before the sprouting of the tubers. Occasionally even 

 in ungerrainated tubers one happens upon powerfully developed 

 bundles or groups of bundles, which only with difficulty may 

 be proved to be activity-hjrperplasicis. 



Vochting^ s^ experiments furnish supplementary data, since 

 they prove that by means of a definite kind of eKperiment.al in - 

 terference . , hypgrplastioal ly developed vascular bundle s may ao- 

 tually be produced. He succeeded in interpolating the potato 

 tuber as an element in the potato plants grown from it. The 

 tuberH were planted upright in the ground, to half their depth, 

 and either developed leaved shoots above the gtound and stolons 

 with abundant roots below it, on which new tubers were formed, 

 or the parts above ground were caused to form root ^, by suit- 

 able expedients: the formation of stolons, however, was possible 

 only on the p&rts under the ground. In the latter case the cur- 

 rent of the ajBsimilate flowed throiigh the tuber to the newly 

 formed stolons and daughter tubers; in th« former the current 

 of water flowing from the root-bearing stolons to the leaf- 

 shoots traversed the old tuber the length of life of which was 

 in both cases appreciably increased/ The anatomical changes 

 in the vascular bundles of the tubers correspond in all. essen- 

 tials to deVries » discoveries. I»ike the potato tubers those of 

 Oxalis crassioaulis may be interpolated in the main stock of 

 the newly produced plant . 



Vochting assumes th§t, in the abnormally constructed tubers 

 which he investigated, the current of water and of nutritive 

 substances caused the increase of the vascular elements, that 

 further the increased mechanical demand also caused the increase 



^ My experiments were interrixpted after possibly a year, 

 i consider it probable that positive results woiild have been at- 

 tained in a longer experimental period, 



^ tJeber die Bildiing der Knoll^n. Bibl. Bot., 1887, Heft 4, 

 p* 11 ff. Zur Phya. der Knollengeifachse. Pringshejin's Jahrb, 

 f. wise. Bot.. 1900, Bd. XXXIV, p. 15 ff. 



