436 Boodle. — The Mode of Origin and the Vascular Supply of 
of the rejuvenated portion of the epidermis, combined with the trans- 
ference of water, required for the enlargement of the rudiment and for the 
production of hairs on its surface. 
Goebel, 1 referring to the production of these .adventitious leaves in 
Cyclamen , states that, as far as is known, they arise directly on the 
hypocotyledonary tuber, and this certainly appears to be the case, nothing 
suggesting the preliminary differentiation of an adventitious stem-apex 
having been observed. Goebel, moreover, regards the production of 
adventitious leaves as indicating the ‘ embryonic ’ nature of the hypocotyle- 
donary region of the seedling. 
Certain exogenous buds and roots may be compared with the 
adventitious leaves of Cyclamen , in that they also require the formation of 
a vascular connexion across the cortex. In Aristolochia Clematitis adven- 
titious buds are formed on the roots, and according to Beijerinck’s 
description 2 they show some interesting analogies to the adventitious 
leaves of Cyclamen. Thus the differentiation of the bud-trace proceeds 
centripetally through the cortex of the root, and forking of the trace occurs 
(Beijerinck, Fig. 82). Further, the epidermis of the bud may vary in origin 
according to the early or late development of the bud, being derived from 
the outermost layer of the root, or from the next layer beneath. 3 
Beijerinck adds that the chief part of the bud arises from the two or 
three layers of cells which immediately adjoin the ‘epidermis’, and may be 
regarded as cork-meristem. 
The formation of exogenous adventitious buds on the hypocotyl has 
been recorded in species of Linaria , Anagallis y Euphorbia , and other 
genera. 4 In these cases the hypocotyl is of normal form, not tuberous as 
in Cyclamen , and the production of the buds may be spontaneous, but is 
favoured or increased by the removal of the cotyledons and stem-apex of 
the seedling, or by encasing these in gypsum, or by the accident of the 
cotyledons remaining enclosed in the seed-coat. 5 As adventitious buds do 
not appear to occur on the epicotyl of these plants, a pronounced formative 
property may be taken as here characterizing the hypocotyl. The pro- 
duction of adventitious leaves by the tuber of Cyclamen may be classed 
with the foregoing cases as another example of an active hypocotyl, and 
1 Goebel : Einleitung in die Experimentelle Morphologie, 1908, p. 205. 
2 Beijerinck : Beobachtungen u. Betrachtungen iiber Wurzelknospen u. Nebenwurzeln. Natuurk. 
Verh. Akad. Wetensch. Amsterdam, vol. xxv, p. 107. 
3 Beijerinck, loc. cit. : ‘ Die dunkelschwarze, Rinde und Knospe iiberziehende Epidermis wird 
gewohnlich durch die Knospe durchbohrt, allein bei sehr friih angelegten Knospen ist die Epidermis 
der Mutterrinde ein integrirender Theil der Neubildung.’ 
4 Goebel : loc. cit. 
B Kiister : Beobachtungen iiber Regenerationserscheinungen an Pflanzen. Beih, z. Bot. Centralbl., 
vol. xiv, 1903, p. 316. Burns and Hedden : Conditions influencing Regeneration of Hypocotyl. 
Ibid., vol. xix, 1906, p. 381. 
