SNAIL- AND SLUG-POLLINATED PLANTS 79 
tion is out of the question, and that pollen can only be transferred by 
snails. 
Warming (Jahrb. Bot., Leipzig, iv, 1883, pp. 328-40), who made his obser- 
vations at Lagoa Santa, traverses this view and argues that snail-pollination is 
impossible owing to— 
1. The rarity of snails in the locality mentioned (Lagoa Santa). 
2. The isolated occurrence of the plant there. 
3. The short flowering period, and the extremely rare occurrence of several 
spadices blooming on the same plant. 
4. The discharge of carbonic acid gas observed by Ludwig within the spathe. 
Warming establishes the fact that at the time of pollination a sticky juice is 
secreted, so that even dry-bodied animals can effect pollination. He is of opinion 
that fertilization is effected by pollen of the same spadix. 
In opposition to this view of Warming, Ludwig holds (Kosmos, i, 1884) that 
the observations of the former were carried out in a place where the plant occurs 
very sporadically in the tops of tall forest trees, and therefore not in sufficient abun- 
dance to attract the characteristic agents of pollination. 
Ludwig accepts the supposed occasional malacophily of our native Lemnaceae : 
snails (and insects) wandering about on the patches of duckweed break off pollen- 
grains and bring them to the concave stigmatic surface. This plant does not need 
to employ any special allurement; without any display, and without any other 
inducement than a firm substratum, it achieves what ‘flowers’ achieve by beauty, 
honey, pleasant odour, &c., which at times serve to attract unbidden guests. Duck- 
weeds like Aroids (according to Stahl, ‘Pflanzen und Schnecken,’ Jena, 1888) are 
protected by raphides against the attacks of snails (cf. Ludwig, ‘Lehrbuch der 
Biologie der Pflanzen,’ p. 544). 
In a few European species pollination by snails actually occurs as well as 
pollination by insects. E. Warming (Bot. Tids., Kjébenhavn, ii, 1877) observed, for 
instance, that the inflorescences of Calla palustris', which are chiefly visited by 
small flies, are also frequented by snails which, crawling up on several inflorescences 
placed one behind the other, transfer pollen-grains that have stuck to the slimy 
surface of their foot to the stigmas of other plants. Hermann Miiller observed 
(‘ Fertilisation,’ p. 246) something similar in the case of Chrysosplenium alternifolium. 
Besides flies, beetles, and ants, he found on numerous flowers small snails (Succinea), 
some creeping about, others devouring styles or stamens. Pollen-grains were usually 
to be found in the slimy tracks that occurred on the flowers, and in several cases 
it was obvious that pollen had been transferred to the stigma by snails. Ludwig 
(SitzBer. Ges. natf. Freunde, Berlin, 1889, pp. 16-18) observed that Chrysan- 
‘In the garden of the Ober-Realschule at Kiel, I observed (on August 4, 1897) a young 
specimen of Helix hortensis on the flowers of the species described as Calla maculata. The snail 
crawled about on the inflorescence, and examination of its foot showed the presence of pollen-grains, 
so that the possibility of the transference of pollen by snails is proved for this Aroid too. I observed 
at the same place (on September 23, 1897) the small slug Limax cinereus (?) among the flowers of 
Colchicum autumnale. It devoured the perianth leaves, and in doing so occasionally disturbed 
anthers and stigma, so that self- or cross-pollination might result. Numerous flowers were almost 
completely deprived of their perianth by slugs, so that frequent visits may be inferred. 
