153 



(170) Of other plants^. In most of the woody plants, whose cuttings 

 I investigated, an obvious difference between basal and apioal 

 poles could not be proved. As yet, no case is known to me, in 

 which, the apical end of sprout -cuttings of any certain spe- 

 cies v?aR the one preferred. However, I do not consider It at 

 all impossible that further investigations raay mfUce known ex- 

 ceptions of this kind (compare that said belov; concerning 

 roots), • ^ 



4 ^^In Populus, Rosa and others, polarity may be recognized 

 In the tissues derivatives of the cambium. {Dhe question as 

 to whether other kinds of tissue may show the same difference 

 In their callus products deserves still -closer investigation. 

 As yet, in the formation of bark callus, I hr^ve ntticed a pre- 

 ference for the basal pole only In cuttings of Alnus. 



Polarity as found in pieces of the stem mniy also be proved 

 in other organs. Petioles of Populus form r. more prolific cal- 

 lus on the pole nearer the place of insertion of the leaves 

 than on the pole toward the leaf blade* Among leaves, thepre- 

 viously mentioned cotyledons of the Cucurbitaceae (Cuo^imis, 

 Luffa and others) have been proved well adapted for this. If 

 the seed leaves of the young plants are removed, cut across 

 and kept in moist air, they form abundant callus tissue on the 

 wounds of the ribs. The difference between the basal and api(i 

 cai pole is unmistakable at the place of the cross sectioning; 

 the injured surface tov/ard the base forme callus very abundant- 

 ly, toward the apex very sparsely. 



Among roots, I have investigated especially those of the 

 dandelion ( Ta r axa cum o f f i c ina le ) which, as is wellknown, may 

 easily b© propagated by root-cuttings^, if pieces of roots, 2 

 to 3 cm. in length, are put into a moist place in sxich a way 

 that both cut surfaces remain exposed to the air, an effect of 

 polarity is evident in the formation of the callus taking placA 

 soon, since almost all isjieces of the roots develop aallxis masses 

 first of all on the basal part, i. 8. on the side toward the 

 root neck, while the apical end remains for the present free 

 from callus, and participates only later in its formation* 

 Rechinger (loc. cit.) also proved polarity of the same kind in 

 other kinds of roots. According to his investigations, root 

 cuttings of Me di cage sativa form a striking exception, a power- 

 ful tuber-like callus is produced on the root end, while the 

 callus oh the sprout end remains small. 



1 De Vries, Ueb, Wundholz. Flora, 1876, Bd. LIX, p. 2. 

 Vochting, Organbildungen im Pflanzenreich, 1884, Bd. II. Barth- 

 elemy, De I'infl, de la tension hjrdrostatique et de ses varia- 

 tions s. 1. raouvement des liquides d. 1. j^eg. etiS. Mem. Acad. 

 Sc. Inscr. Bell, Lett. Toulouse, 1881. Muller, N. J. C, Kul- 

 turversuche an Weidensteckl, Ber. d. D, Bot. Ges., 1885, Bd, 

 III, p. 159. Kny, Umkehrversnche mtt Ampelopsis quinquefolia u, 

 Hedera helix. Ibid,, ^889, Bd, VII, p. 201. Tittmann, who 

 worked also with poplar cuttings, seems to have overlooked this 

 polarity. If itis a question in any investigation of obtaining 

 the most luxuriant callus excrescences possible in a short time, 

 it is advisable to place the cuttings upside down. The callus 

 formations described above (compare fig. 60) originate from 

 cuttings inver-sely oriented, 



^ Compare Wiesner, Elementarstruktur, 1892. p* 112 ♦ 

 Rechinger, 1 oc^ cit. 



