Hill . — Studies in Seed Germination. 219 
where the root and the tube of the petioles are united, and is found to 
indicate the position of the plumule and the commencing tuber. With 
the development of the root, the petiolar absorbing hairs dry up and 
cease to function. The tube of the petioles in the specimen grown at 
Kew was from 5 to 7*5 cm. in length, but under natural conditions it would 
no doubt penetrate to a greater depth in the soil. The plumule now 
commences to elongate and breaks through the petiolar tube near the base, 
the tube splitting under the pressure into its component halves. The split- 
ting apart of the petioles extends gradually upwards towards the cotyledons, 
until at length only a small portion of the tube is left intact (cf. Fig. 8). 
The apex of the plumule is sharply bent over at the tip, and this 
strong curvature of the shoot apex is maintained by the mature shoot 
and may perhaps be attributed to the fact that the plant is a scrambling 
climber aver and among bushes. 
With the growth of the plumule and its appearance above ground, 
accompanied by the production of green leaves, the tuber begins to increase 
in size, and in particular to broaden at the apex. As a result the cotyledon 
petioles each become split into three portions which, owing to the continued 
expansion of the tuber, gradually get separated somewhat widely apart, 
and the young tuber when dug up is seen to be suspended from the seed by 
six separate strands, the split petioles of the two cotyledons (PL V, Fig. 9). 
The base of each strand is swollen out and passes gradually into the tuber, 
which in some cases may appear to be composed of six semi-independent 
portions. The young tuber has also been found to be deeply cleft into two 
from below, the two halves roughly corresponding to the two cotyledons and 
having been supplied by the materials stored in each (cf. Fig. 9). 
Within the bases of the cotyledon petioles, the tuber develops a some- 
what flattened-oval area with the shoot rising from the midst, and on this 
flattened surface several dormant buds are developed, which no doubt would 
give rise to aerial shoots should occasion require. 
Internal Structure of Petioles. 
An examination of the petiole tube in transverse section shows usually 
six vascular bundles, three belonging to each petiole, and if the section be 
of a petiole tube which has already split into its component portions it is 
noticeable that the cotyledon petiole shows grooves which correspond to 
the spaces between the vascular bundles (Text-fig. 1). As the tuber in- 
creases in size, these grooves are seen to be the planes of weakness along 
which the petiole will split into strands, as already described, so that each 
strand will contain a single vascular bundle. 
It is of interest to notice that owing to the splitting apart of the 
petiole tube into its component halves, the edges formerly in union must, 
when free, be furnished with a ‘ false ’ epidermis. No new 1 false ’ epidermis,. 
