36 INVASION 



rains, etc., and the other comprising winds, animals and 

 man. Halt {i&&6:ht) ande&vored to show that moss spores 

 and, in consequence, the spores of all cryptogams are not 

 disseminated by the wind over great stretches. His evi- 

 dence, however, is drawn entirely from distribution, with 

 little regard to the unique importance of ecesis, and hence 

 it affords no real support to his contention. He has made 

 much of the fact that the mosses which invade a denuded 

 area are mostly drawn from neighboring formations, but 

 this signifies merely that the wind carries the greater 

 number of spores a short distance rather than a long one. 

 Huth (t887) wrote a comprehensive treatise upon hooked 

 and retrorsely barbed fruits, enumerating the examples in a 

 long list of families and indicating their relation to distribu- 

 tive agents. Dingier (1889 :33I) investigated the comparative 

 transportability of wind-distributed seeds' and fruits, as de- 

 termined by their velocity in falling. As a result of his ex- 

 periments, he made the following division of disseminules : 

 (1) dustlilie, Micrococcus, spores, Lycoperdon; (2) grainlike, 

 Papaver, Sibbaldia; (3) bladder-inflated, Astragalus, Ostrya. 

 (4) filiform, Bromeliaceae; (5) disciform. Iris, Ulmus; (6) con- 

 vex-disciform, Ptelea; (7) parachute-like. Taraxacum, Vale- 

 riana, Asclepias, Salix, Dryas, Pulsatilla; (8) winged-turbin- 

 iform, Eumex; (9) elongate-lamelliform, Ailanthus, Tecoma; 

 (10) elongate-lamelliform, seed at the side, Bignonia; (11) 

 elongate-lamelliform, seed at the end, Fraxinus; (12) elon- 

 gate-lamelliform, seed at end but one side also weighted, 

 Acer, Pinus. Wiesnet (t889:I05) summarized briefly but 

 somewhat comprehensively the subject of migration, while 

 Drude (1890:100) touched it in a more general way. 



Kemer (t 892:79 1) has furnished an account of dissemin- 

 ination which rivals that of Hildebrand. The wealth of de- 

 tail especially is something extraordinary. Disseminules 

 are grouped under two main heads: offshoots, and fruits 

 and seeds, though the author recognizes that whole plants 

 are sometimes distributed. Under offshoots are considered 

 mycelia, protonemata, roots, root-stalks, runners, hormo- 

 gones, zoogonidia, soredia, gemmae, buds, etc., while their 



