4 1 6 Hill ’ — The Morphology and Seedling Structure of the 
of these little leaves, two or three together, but in such cases no starch was 
seen and they thus appear to be rather of the nature of water stomata. In 
either case it is difficult to see that they can be of any value to the 
absorbent cotyledon, since its lamina is never withdrawn from the seed. 
Finally, in the persistence of the primary root for some time after the 
formation of the bulb (cf. Figs. 7-10, PL XXIX, &c.), we have additional 
evidence of the essentially dicotyledonous character of these seedlings. 
The Geophilous Habit. 
The species of Peperomia under discussion are confined to the high 
mountain regions of the Andes and of Central America, and in their adult 
forms they show different biological adaptations, which no doubt represent 
their response to the peculiar xerophytic conditions of their several locali- 
ties. Adaptation to new conditions must have appeared first in the adult 
structure of the plant, and the tendency to bulb production must be due 
to the shortening of internodes ; but, it seems clear, from the consideration 
of analogous cases, that changes, leading eventually to the evolution of 
acaulescent forms, may take place without any appreciable effect on the 
structure of the seedling 1 . With further advances towards geophily, 
however, involving, e. g. the formation of a swollen stem-structure in 
definite response to xerophytic conditions, the initiation of the necessary 
structural modifications of the adult would begin to be thrown back more 
and more into the early stages of the plants development, until finally the 
structure of the embryo itself would become involved. 
It is obviously of paramount importance to a plant if the conditions 
are severe — such as, e. g., the occurrence of a long dry season — that a bulb 
shall be formed by the young seedling as quickly as possible, and in the 
most economical way 2 . We must suppose such changes to have been 
brought about in the seedling — which I am considering to be dicotyle- 
donous-in response to the xerophytic conditions of the situation. The 
almost universal method in which this problem of bulb-formation has been 
solved is by the rapid transference of the reserves of the seed into the 
tissues of the hypocotyl, which in its turn has become adapted to receive 
them. The urgency of making an underground storage as rapidly as 
possible has no doubt been the exciting cause for a division of labour 
between the cotyledons. In the geophilous Peperomias, one cotyledon has 
been found to be capable of performing efficiently the functions of absorp- 
tion 3 , whilst its fellow has acquired the equally important function of 
1 Cf. Primrose, Kohl Rabi, Plantago , &c., &c. 
2 The special biological advantages accruing from the adoption of the geophilous habit are 
clearly stated by Miss Sargant in her paper, Ann. Bot., xvii, 1903, pp. 79 and 80. 
3 Cf. Cyclamen , where only one cotyledon is developed 'which absorbs the reserves in the seed, 
whilst the other remains rudimentary. 
