139 



Prom the statements of Vochting: here quoted, it is ob- 

 vious that the tissue excrescences which he ohserved should 

 be ascribed to kataplasmas. 



Sachs^^Was the first to produce correlation-heteroplas- 

 mas experimentally. "If all vegetative sprout points be re- 

 moved from vigorously growing pumpkin plants f Cuourbltc mlxlma ) " 

 a very remarkable phenomenon occurs which Is as vet unexplained, 

 (153) the embryonic root colls, present In the tissue of the stem 

 at the right and left of each petiole, grow out Into short 

 stalked tubers as Irrge as hazel op v/alnuts, in which the roof 

 cap disappears and the vegetative point becomes Irrecognlaable , 

 ?/hlle the axillary fibro-vasoulsr cord (the axillary cylinder 

 of the root) is resolved into a circle of isolated vascular 

 bundles, separated by ground tissue which contains chlorophyll." 

 Sachs calls attention to the similarity between the norrnal 

 structure of the axle and that of the abnormal Cucurblta tuber; 

 I think thr.t no special conclusion maybe drawn from this db 

 to the character of the new formation. That roots may become 



freen Is r. wide-spread phenomenon, already described above 

 p. 56), The other histological characteristics, distinguish- 

 ing the tubers from normal roots, seem to me connected with 

 the overproduction of undifferentiated parenchyma, recurring 

 In so many heteroplasmas. 



Further Investigations will show whether all plants can 

 at 7;111 be brought to the formation of cor relation -heteroplas- 

 mas or whether those plants tend especially to this kind of ex- 

 crescence which form parench37matlc, little differentiated tis- 

 sue-masses ("tubers") even Im a normal course of development. 

 That the ability to develop correlqtion-heteroplasmas is not re- 

 stricted to tuberous plants is shown by the oases Just discussed, 



C. Kraus^ using Helianthus, attempted to Influence the 

 processes of growth by removing the apices of the plants under 

 experimentation. According to him, wart-like petiole excres- 

 cences are formed on the stalks virhich have no Inflorescences, 

 C, Kraus also makes dome statements concerning the anatomical 

 structure of the plants operated upon. In similar experiments 

 Woilny^ found that the axillary buds were transformed Into 

 tuber-like rolls. 



It must be left undecided whether the "gnarled tubers", 

 occurring on various Eucalyptus species, are to be reckoned 

 among correlation-heteroplasmas. Some notes concerning these 

 may be found in secjrion 3, whieh treats of wound-wood, 



2. Callus 



Leaving out of the question the products of the processes 

 of restitution, we have termed all cell and tissue forms, pro- 

 duced after and as a result of injury, callus formations in 

 the widest sense of the woord and have spoken of them repeated- 

 ly. In many plants and plant organs only a metaplastic change 



^ Gesaram. Abhandl,, Bd, II, p. 1172, 



^ Kunstl. Beeinfl. des specifischen Bildungsganges von 

 Helianthus annuus durch EntblStterung H, s. w. Forsch. Beb. 

 d. Agrikultur Physik, Bd. IV. 



^ Einfl, d, Entgipfelns der Pfl. auf deren Entwickelung 

 und Produktionsvermogen. ;Lbld^, 1885, Bd. VIII, p. 107, • 



