AGGREGATION AND lAIIG RATION 



245 



1. Water (hydrochores). This group comprises all plants dis- 

 tributed by water whether in the form of ocean currents, tides, 

 streams, or surface run-off. In the case of streams and run-off 

 especially, the nature of the modification is of little importance, 

 provided the disseminules are impervious, or little subject to injury 

 by water. Motile plants, or those with motile cells, belong entirely 

 to this group. 



2. Wind (anemochores). The group of wind-distributed species 

 includes practically all terrestrial plants in which modifications 



Fig. 98. Migration of the immobile seeds of Corispermum by means of 



surface drainage. 



for increasing the surface of seed or fruit have been greatly developed, 

 or in which the part carried is minute. Sack-like, winged, hairy, 

 parachute, pappose, plumed, and some awned seeds or fruits 

 are the various types of modification for wind-distrilnition. 



3. Animals (zoochores). Animals distribute seeds in conse- 

 quence of attachment, carriage, or use as food. Dissemination 

 by attachment has been specialized in a higii degree. The three 

 types of contrivances for this purpose are found in spinose, hooked, 

 and glandular fruits. Distril)Uti<m ])y swallowing and tliai by car- 

 riage often play a striking })art on account of the great distance 



