STUDIES IN PLANT REGENERATION 199 
(Daucus Carota), turnips (Brassica Rapa), salsify (Tragopogon 
porrifolius), radish (Raphanus sativus), and parsnip (Pastinaca 
sativa) were next used; and as an example of a woody root, 
Pelargonium radulum was selected. Іп these roots, attempts were 
first made to determine whether the part had any power to regen- 
erate, then to solve the question of the tissues involved, and 
finally to secure evidence as to the action of external conditions 
and polarity in producing the structures. 
Rechinger * used the root of the horseradish (Roripa Armor- 
acia) to determine the minimal size of the piece capable of regen- 
eration. The horseradish has on its surface, at the indentations 
left by the emergence of the secondary roots, little swellings. To 
these the name “ buds ” cannot be strictly applied, because, though 
the cells are rich in protoplasm, and evidently are “ embryonic ” 
in nature, there is no vegetative point as such present before 
growth begins. This develops, however, within a few days after 
planting the roots or using pieces as cuttings. The shoots thus 
formed, therefore, would not be classed under true regenerations, 
according to the definition. A transverse piece of the root, not 
more than 1.5 mm. in height was found by Rechinger to be cap- 
able of forming a new plant. Аз to longitudinal sections, he says, 
“Ist noch eine Sprossanlage vorhanden, so wird dies bald ausge- 
bildet ; sind nur das Cambium und die Gefassbiindeln vorhanden, 
so kommt es über die Callusbildung nicht hinaus." He goes on to 
show, further, that when such slices pass through the rind, be- 
tween the epidermis and the cambium ring— thus cutting the 
bundles which branch out to the buds — new shoots are formed at 
these intersections without previous callus formation. 
In confirming these results, some additional information as to 
the regeneration in the roots of horseradish was secured. 
Experiment 1.— A large number of transverse preces алы” 
mm. in height were used as cuttings. Many of these, besides ie 
veloping the buds already present on the rind, formed shoots. e 
novo, from the cambium of the upper or loner И 2 Е 
differently, and occasionally from both. Usually when от ка 
аге already present оп a cutting, their development xw js : 
production of others. Неге, although in some — нида 
- Si HS РОТ Т А 
* Rechinger, С. А с. 322. 
е 
