MIGRATION 35 



Hildebrand( J 873) brought together the results of various 

 observers in a treatise on dissemination, which is still the 

 most extensive and the most important in this field. He 

 divided distributive agents into winds, water, animals, 

 dessication, and developmental features which effect distri- 

 bution, such as turgescence, growth and motility, making 

 a minute analysis of the contrivances under each. He 

 classified contrivances for wind distribution as: (a) small- 

 ness and lightness, (b) winged structures, (c) hairy and 

 feathery modifications of the seed, fruit, style, peduncle, 

 rhachis or glumes. Adaptations for water distribution are 

 relatively few, consisting mostly of air-containing tissues or 

 organs. Animal-distributed parts are divided into: (a) 

 fleshy fruits, (b) hooked fruits and (c) glandular fruits. The 

 author furthermore discussed the significance of the lack of 

 useless modifications, the distribution of dissemination con- 

 trivances in the various groups and their influence upon mi- 

 gration. Grisebach (1877:4) established a fundamental law 

 of barriers as follows: "La loi supreme servant de base a 

 r^tablissement persistant de flores naturelles, doit done Stre 

 reconnue dans les barriferes quienont entrav^[ou complete - 

 ment empSch^ le melange, " and he illustrated its application 

 briefly in a few general cases. He considered the general 

 facts of migration of arctic-alpine plants and of forest and 

 steppe plants, but more with reference to the interchange of 

 species between regions than with respect to the methods 

 and agents^in dispersion. Comber (1874:248) endeavored to 

 relate modifications for dissemination, such as coma, pappus, 

 spines, etc. to the geographical area of the species of the 

 British flora, but, while this method deserves a more 

 thorough trial, his results are too conflicting to be of much 

 value. 



An extremely important contribution to the subject is that 

 of Englef (t879), but as this work deals with invasion as a 

 whole rather than with either of its parts, migration or 

 ecesis, consideration of it will be reserved for another place. 

 Goeze (1882:96) grouped migration agents in two classes, the 

 one including the various aqueous agents, currents, streams. 



