228 
James Small. 
differentiation, morphological differentiation during the life of the 
species, etc. Such a comparison has not yet been made. 
The results of the present investigation which will be valuable in 
the subsequent study of the geographical distribution of the 
Compositae are (1) that the ordinary pappose fruit under the proper 
meteorological conditions can be blown many hundreds of miles 
over land or sea, (2) that hypothetical land bridges are not 
necessary to explain the present distribution of the Compositae, so 
that we can take the world as it is without raising and sinking 
continents, as Darwin (10) says “ in a quite reckless manner. ” This 
latter is an important point as the Compositae are almost certainly 
of such recent origin that the possibility of land bridges is in many 
cases quite out of the question. 
In order to facilitate reference the following summary is given 
of the minimum velocities of wind necessary for the dispersal of the 
species investigated, together with the expressions for winds of such 
velocities (cp.46. p. 161) 
Table XI. 
Species. 
Experimental 
Value 
in m.p.h. 
Calculated 
Value 
in m.p.h. 
Common Name of 
Wind. 
Taraxacum officinale, Weber 
2-06 
1-97 
Light Breeze. 
Seneeio vulgaris, L. 
Senecio vulgaris, L. 
1-48 
1-25 
Light Air. 
var. radiatus erectus, Trow 
1 -76 
— 
Light Breeze. 
Tussilago Far/ara, L. 
•59 
— 
Less than a Light 
Air. 
Centaurea imperialis, Hausskn ... 
7-2 
7-3 
Moderate Breeze 
Ursinia speciosa, D.C. 
4-5 
4-7 
Gentle Breeze. 
Leontopodium alpinum, Cass 
4-4 
— 
Gentle Breeze. 
BIBLIOGRAPHY IX. 
1. Beauverd, G. Quelques cas de dissemination des graines par le vent. 
Bull. Herb. Boiss., Ser. 2, Vol. I, pp. 633, 1901. 
2. Beccari, O. Beitriige zur Pflanzengeographie des Malayischen Archipels. 
Abst. by Engler, A. in Bot. Jahrbiich. Bd. I, 1881. 
3. Beeby, W. H. The Scape of Taraxacum. Journ. Bot., Vol. 46, p. 120, 
. 1908. 
4. Berget, A. The Conquest of the Air, pp. 46-47. London, 1909. 
5. Bessey, C. E. Weight of Dandelion-down. Science, N.S. Vol. XX, 
p. 119, N.Y. 1904. 
6. ,, ,, Plant Migration Studies. University Studies. Univ. 
of Nebraska. V, pp. 1-27, 1905. 
7. Blackman, V. H. and Knight, R. C. A Method of Controlling the Rate 
of Air Movement in Transpiration Experiments. 
Ann. of Bot. Vol. XXXI, p, 216, 1917. 
