Bums and Hedden, Conditions infiuencing regeneration of hypocotyl. 391 
In all tliese cases there is a hindrance to the normal move¬ 
ment of materials in the plant — organs which normally fnnction — 
have ceased either entirely or partially to do so, in one case 
from internal, in the others from external canses. That is, the 
prodnction is dne to correlation and not to the wonnd. 
2. The experiments confirm the observation of Gloebel 4 ) 
that embryonic tissne reacts easier than old tissne. The yonng 
hypocotyl is apparently able to prodnce a bud from every part 
of the epidermis. This ability gradually is lost as the plant 
gets older. In old plants however, this ability is retained by 
the part nearest the base, that is the oldest part of the hypocotyl. 
This part is especially predisposed to produce bnds. Even in 
the yonng plants the first bnd nsnally appears nearer the base 
than apex of the hypocotyl of decapitated seedlings. 
It was not determined whether or not any special cells in 
the epidermis differed from others in complexity of strnctnre or 
amount of protoplasm contained as. is the case in certain leaves. * 2 ) 
3. Polarity. Decapitated seedhngs do not show polarity. 
The origin of the first buds in many cases is toward the base 
of the hypocotyl. The origin of the bnd at base of the old 
plant confirms this also. 
Unter the paragraph on light however, we saw that ..pola¬ 
rity-* became very marked in Linum when the npper part of 
the decapitated seedling was strongly illnminated. Withont light 
and a relatively strong light, regeneration did not take place. 
The fact has been noted in other cases that bnds were 
prodnced only on the light side. Ön the other hand Horn- 
schnck tliinks that weakened illnmination may be a factor in 
the development of bnds on leaf of Malaxis palndosa, a snggestion 
with which Gloebel does not agree. 3 4 ) 
In many cases Gloebel 4 ) has pointed ont the relation of 
the place of origin of „adventitions“ bnds to the fibrovascnlar 
bnndles. This is seen in case of Begonia Rex, TJtricularia , Car- 
clamine pratensis. (See illnstration.) 
The facts observed on seedlings with the light experiments 
seem to rnn parallel with these. The bnndles are the places 
throngh which material is moving. In onr yonng seedlings the 
bnndles are not well developed. AVhen however, the cotyledons 
are removed or cease to fnnction, their work is taken np by the 
epidermis. The cells of this develop a vast arnonnt of Chloro¬ 
phyll and ah movement is to and from thera. Very soon after 
they originale one or more are connected with the condncting 
System, the others perish. Only those cells exposed to light, 
fnnction as the cotyledons and hence all flow of material is to 
and from the lightest side. Light is then an indirect canse of 
J ) G o e b e 1, Über „Regeneration im Pflanzenreich^. (Biol. Centralbl. 1902.) 
Willkürliche Entwicklnngsänderungen bei Pflanzen. Jena 1903. 
2 ) KlebsRegenerationen bei TJtricularia. Bd. 93. p. 118. 
3 ) — Flora. 93. p. 118. 
4 ) Biol. Centralbl. Flora. 93. etc. 
Beihefte Bot. Centralbl. Bd. XIX. Abt. I. Heft 3. 
27 
