122 TRANSACTIUNi!, NATUKAI, IlISTOKY SOCIETY OF GLASGOW. 



of the hooked and sticky class of seeds now 

 dependent on animals for dispersion were originally- 

 plumed or winged, and that provisions at first 

 useful in securing delivery have been turned to 

 account in promoting transport. 



By animal agency seeds are more likely to be 

 delivered in situations favourable to development 

 than by the wind. Herds of graminivorous creatures 

 natvirally frequent districts adapted to the growth 

 of grasses. It is therefore an advantage if the 

 plants can avail themselves of the animals as agents 

 for the transport of their seeds. On treeless steppes 

 and prairies the scarcity of birds renders coloured 

 and pulpy fruits less available as means of dispersion. 

 Under these circumstances a mutual advantage is 

 reaped when plant and animal seek new pastures 

 in company. 



9. Snails. — According to Delpino, snails effect the 

 fertilisation of certain flowers. The spathe of 

 Alocasia odora has an upper and lower chamber. 

 The latter, from which the odour emanates, contains 

 the pistils. In the first stage snails are admitted to 

 the lower chamber, but the entrance afterwards 

 closes ; and in the second stage they are only 

 permitted to enter the upper chamber, which 

 contains the male flowers. Alocasia is thus seen to 

 be protogynous and to be fertilised with pollen 

 from older flowers. It is Delpino's opinion that the 

 visitors, after effecting fertilisation, are poisoned by 

 an acrid secretion formed inside the spathe, and are 

 so prevented from devouring the flowers. Delpino 

 mentions a number of other Aroids fertilised in this 

 manner. In Rliodea japonica, one of the Liliaceee^ 

 the fleshy perianth seems to provide entertainment 

 for the gasteropods, so that they are not under the^ 

 necessity of injuring the essential organs of the 

 flower. The accuracy of Delpino's conclusions in the^ 

 case of this plant admits of no doubt, for its fertili- 

 sation by Helix aspera and H. vermiculaHs has. 

 actually been observed. The peculiar manner in' 



