428 Hill . — Studies in Seed Germination . 
decapitated hypocotyledonary tuber are still in the f embryonic ’ condition 
and are comparable both physiologically and morphologically to the 
cotyledons. 
Older tubers which had given rise to plumular leaves were also 
decapitated for comparison with the seedling tubers, but it was found that 
in such cases the adventitious leaves were produced not from the edges of 
the cut tubers, but from the cut surface itself close to the centre of the 
tuber (PL XX, Fig. 6). These leaves were plumular in appearance, and 
were found to behave as do the normally produced plumular leaves. New 
laminae could not be produced from the petioles when the original laminae 
were removed, nor could the leaves be induced to form roots when treated 
as ‘ leaf cuttings though they formed a callus in the same manner as do the 
plumular leaves. 
In both the decapitated seedling and adult tubers one or more 
plumular buds will develop in course of time and apparently normal 
Cyclamen plants result. The tubers become rounded above by the growth 
of the tissues of the tuber which are protected by corky tissue. They 
differ, however, in most of the cases examined in having several plumular 
shoots instead of the single axis developed by normal plants (PL XX, Fig. 7). 
Summary. 
Arguments have been brought forward on morphological grounds to 
show that the rudimentary curved body lying opposite the cotyledon 
proper in the Cyclamen embryo is the second cotyledon, and that under 
ordinary conditions it does not develop to form a green leaf. 
When artificially induced to develop, however, it is found to respond 
to the traumatic stimulus of the removal of the lamina by regenerating 
a new lamina or laminae from the petiole, exactly as does the normally 
developed first cotyledon. 
The evidence afforded by this power of regeneration may therefore be 
accepted as definite proof that the embryonic rudiment is undoubtedly the 
undeveloped second cotyledon. 
The Cyclamen seedling, though aberrant in type, is thus seen to be 
truly dicotyledonous in nature. 
Thus, though the second cotyledon of Cycla 7 nen has ceased to function 
as an absorbent organ in the seed, possibly in correlation with the geophilous 
habit of the genus, it is of interest to find that, when stimulated to develop 
as an assimilating organ, it is in the physiological state characteristic of and 
peculiar to the cotyledon proper — a condition which is not shared by any of 
the plumular leaves which arise subsequently from the shoot. 
It has also been found that the leaves adventitiously developed from 
the edge of decapitated seedling tubers — the swollen hypocotyl — respond 
to traumatic stimuli in precisely the same manner as do the cotyledons. 
