Hill. — She dies in Seed Germination. 
42 1 
■pi'- 
Text-fig. 2. C. 
neapolitanum . The 
cotyledonary lamina 
with the seed have 
been removed, and the 
second cotyledon, c. 2, 
is developing. The 
petiole of the normal 
cotyledon, c. 1, is be- 
ginning to wither. 
Hildebrand has pointed out, by removing the lamina of the seed-leaf of the 
young seedling. A more certain way of stimulating 
the rudimentary second cotyledon to develop, however, 
is to remove not only the blade but also the greater 
part of the petiole of the original seed-leaf. The second 
cotyledon is also frequently stimulated to develop if 
by any chance the lamina of the first cotyledon should 
be unable to escape from the seed-coats and so fail to 
function as an assimilating organ. 
The second cotyledon is, as a rule, a smaller organ 
than the first, but otherwise it is very similar in general 
appearance; the apical notch so characteristic of the 
seed-leaf is usually noticeable, and the margins tend to 
be smooth and are not as a rule provided with the 
serrations which are characteristic of the margins of the 
plumular leaves. Conspicuous surface markings, which 
are a feature of the plumular leaves of Cyclamen , are 
also absent from the laminae of both cotyledons. 
The vascular structure of the cotyledonary petioles 
shows some difference from that of the petiole of the 
young plumular leaves, but the differences are not 
constant. In the plumular leaf-petioles, especially near 
the lamina, there is usually a definite reniform stele sur- 
rounded by a distinct pericycle and endodermis and 
enclosing some three to seven radiating xylem groups 
of equal size. 
In both the cotyledonary petioles, however, the 
vascular structure, as Miss Sargant noted for the first 
cotyledon, suggests a double structure. The xylem 
elements are arranged in two well-developed lateral 
groups, especially near the base of the petiole, while near 
the apex a somewhat feeble median xylem group may 
be seen in cross-section. The double type of bundle, 
which to some extent seems to be associated with 
a slender petiole and a small lamina, has also been 
noticed in sections of the petioles of adventitious leaves 
arising from the decapitated tuber . 1 
1 Mr. Boodle, has kindly examined sections of the petioles, and has made the following 
observations : 
‘ In the double bundle there are sometimes two protoxylem groups, one to each xylem mass, or 
sometimes there are three protoxylems, two to the larger group of xylem, one to the smaller. The 
latter case gives an indication of the triple structure attained higher in the petiole by division of the 
larger xylem group, accompanied by displacement whereby one of these groups takes up a median 
position. 
* Where the base of the petiole has a triple bundle there may be three protoxylems, but here, 
Text-fig. 3. C. 
neapolitanum. The 
first cotyledon, c. 1, 
has been unable to 
free its lamina from 
the seed-coat, and the 
second cotyledon, c. 2, 
has developed and ex- 
panded its lamina. 
