MIGRATION 37 



dispersal is treated with respect to motility, growth, water, 

 wind, expulsive mechanisms, animals and man. Under 

 fruits and seeds, there is recognized a large class of sling- 

 fruits in which propulsion is effected by turgidifcy, dessi- 

 cation, torsion or elasticity, and a small group of creeping 

 and hopping fruits. "With respect to agents, Kerner treats 

 of dissemination by water, including drainage, by water and 

 wind, and by wind alone, distinguishing under the latter, 

 rolling and flying fruits, which are flattened, winged, comate 

 or parachute-like. Migration by the agency of animals is 

 by means of deglutition, concealment, or attachment, the 

 latter occurring by means of mud, water, mucilage, gland- 

 ular hairs or barbed processes. Attention is also given to 

 the elongation of peduncles and to other contrivances by 

 which seeds are placed in a position to be more effectively 

 influenced by distributive agents. Excellent monographs 

 of the dissemination contrivances in particular families have 

 been made by Dammer (1893:260) for Polygonaceae and by 

 Buchwald ( t895 :494) for Leguminosae. Pound & Clements ( J898 : 

 t53) grouped contrivances for wind distribution in four 

 classes; (1) comate and pappose seeds; (2) winged seeds; 

 (3) winged fruits ; (4) tumbleweeds. Water distribution is 

 by streams or by surface drainage, while dissemination by 

 means of animals occurs by deglutition, carriage or attach- 

 ment. Schimper (1898:32) has simply considered the general 

 relation of wind and water to dissemination. 



Mobility {mobilitas) denotes potentiality of migration as 

 represented by modifications for this purpose. It corres- 

 ponds, in a sense, to dissemination, though seed production 

 also enters into it. Its most perfect expression is found in 

 those plants which are themselves motile, Bacteriaceae, 

 Oscillatoria, Volvocaceae, and Bacillariaceae, or possess motile 

 propagules, such as most Phycophyta. On the other hand it 

 is entirely undeveloped in many plants with heavy un- 

 specialized seeds and fruits. Between these two extremes 

 lie by far the greater number of plants, exhibiting the most 

 various degrees of mobility, from the motile though almost 

 immobile offshoots of many Liliaceae to the immotile but very 



