476 BOTANICAL GAZETTE [DECEMBER 
ANDREAE, GILTAY, and BuTTEL-REEPEN, he regards color attraction as estab- 
lished in the case of Apis‘and Bombus. However, the experiments of GILTAy 
and ButTEeL-REEPEN show that color becomes less and less a source of attraction, 
when bees become acquainted with the neighborhood which they frequent. 
Again the visits of bees to flowers that are not showy indicate that high coloration 
is not absolutely necessary to secure the visitation. 
ERY also has attempted to find out the exact value of color as source of 
attraction for bees.3? She finds that flowers with colored organs attract bees 
more than do flowers of the same species without colored organs, that honey does 
not serve to attract bees, that artificial flowers attract bees as well as do natural 
flowers, and that perfume attracts but little. The author thinks that she has 
demonstrated that color and form together offer four times as much attraction to 
bees as pollen, perfume, and nectar combined.—H. C. Cow es. 
Apams has publisheds3 another paper on postglacial migration, in which he 
discusses the successive ‘‘waves” of life from the close of the Ice Age until now. 
After the first or tundra wave, there followed a wave from the western and north- 
eastern centers, consisting of peat bog and conifer forest plants and animals. 
The third wave was from the southeastern and southwestern centers, migration 
taking place from the former along the coastal plain and the Mississippi River; 
from the southwestern center there came desert plants and animals. The paper 
concludes with general remarks concerning the definiteness of the laws of migra- 
tion. Invading elements enter a new region at definite places, and they remain 
in definite associations. The succession of ecological associations is similar even 
in diverse regions, where the biotic components are different. A particular merit 
of this paper is that animals and plants are considered together, forming a biota, 
rather than a fauna or a flora—H. C. Cowtes. 
Bessey has continued his studies on the encroachment of the forest upon the. 
Nebraska prairies.3+ After a general discussion of the factors involved in migra- 
tion, instances are given of recent natural enlargements of the forest area. Such 
advances of the forest are to be observed especially where protection is afforded 
from fires and grazing animals. An especially favorable place for the effective 
germination of tree seeds is along a forest border in a moist valley, where tall 
weeds readily develop and choke out the prairie grasses. The forest border may 
advance from a few feet to several hundred feet in a single year. The paper is 
accompanied by maps showing the — within the state of each of the 
native Nebraska trees.—H. C. Cow 
3? WERY, J., Quelques oo sur l’attraction des abeilles par les fleurs. 
Bull. Acad. ‘toy. Belgium 1904: 1211-1261. 
33 Apams, C. C., The Cee dispersal of the North American biota. Biol. 
Bull. 9:53-71. 1905. 
34 Bessry, C. E., Plant migration studies. Univ. Nebraska. Studies 5:1-27 
1905. 
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