78 INTRODUCTION 
(c) Plants with Snail-pollinated or Slug-pollinated Flowers, 
Malacophilae (M). 
The possibility of snails or slugs effecting pollination arises when small flowers 
are crowded together at the same level, and in the case of flat flowers with stigmas 
and anthers which project but little. It is then possible for such creatures when 
creeping over the flowers or inflorescences, to transfer pollen-grains which remain 
clinging to the slimy surface of their foot to the stigmas of the same plant, or 
even to those of others. In most cases, however, snails or slugs are only the 
occasional and not the exclusive agents of pollination. 
The first contribution to our knowledge of malacophilous plants was made 
by Delpino (‘ Ulter. osserv. sulla dicog. nel regno veg.,’ Atti Soc. ital. sc. nat., Milano, 
xi and xii, 1868 and 1869, pp. 238-40) when he described the pollination of Rohdea 
japonica (? Asparagineae) by Helix aspersa, H. vermiculata, and others. Hermann 
Miiller (‘ Fertilisation,’ p. 551) summarizes the passage as follows :—‘ This plant 
seems to be transitional to the Aroideae, for it possesses a kind of spadix with crowded, 
flattened flowers arranged in an unbroken spiral. The flattening of the margin of 
the perianth to exactly the same level as the tips of the anthers and stigmas led 
Delpino to suspect pollination by animals creeping over the flowers, and he actually 
observed snails (Helix aspersa, vermiculata, and others), each of which consumed 
greedily the yellow perianth, which is fleshy at the time of flowering, of about ten 
flowers belonging to any particular spadix, and then visited another inflorescence. 
Only the flowers touched by snails were fertile; the plants appeared infertile as 
regards their own pollen. There can be no doubt from these observations that 
snails are active agents of pollination. 
Delpino (op. cit., pp. 235-8) suspected that Alocasia odora is also pollinated 
by snails; the entire length of spadix, according to Hermann Miiller’s paraphrase 
(‘ Fertilisation, p. 564), is beset with normal and reduced female and male flowers. 
Only the female flowers are enclosed in the lower dilated part of the spathe, and they 
are the first to ripen. There is only a narrow passage by which snails can creep into 
the space surrounding the stigmas, into which they are tempted by the diffusion of 
an agreeable odour. Even this entry is closed in the second stage of flowering, at 
which time the anthers dehisce. Snails which visit flowers that are in this second stage 
seek admission in vain, covering themselves however with pollen, which they deposit 
on the stigmas of younger flowers to which the approach still stands open. After the 
snails have discharged the important work of cross-pollination, Delpino states that 
they are killed by means of an irritant juice in the space that encloses them, being 
thus prevented from devouring the flowers. 
Delpino also supposed that there was occasional transfer of pollen by snails in 
Amorphophallus variabilis, species of Anthurium, Arisaema filiforme, Atherurus 
tripartitus, and Typhonium cuspidatum. 
Ludwig (Kosmos, vi, 1882, pp. 34 et seq.) observed and investigated at Greiz 
‘greenhouse specimens of Philodendron pinnatifidum Scho//., and believes that this 
plant is pollinated by snails. The entire floral arrangement agrees in many points 
with that of Rohdea japonica and Alocasia odora, which Delpino has described as 
snail-pollinated. Ludwig points out that in Philodendron pinnatifidum self-pollina- 
