AGRICULTURAL BOTANY. 129 



fruits. A few weeks after the freezes the herbaceous vegetation appeared nor- 

 mal, while the woody plants had just begun to recuperate. 



The usual typos of recuperation in trees and shrubs were a new crop of leaves 

 when the twigs were uninjured and the terminal bud intact, the appearance of 

 lateral shoots from the leaf axils of uninjured portions when the distal portions 

 of the twigs were destroyed, and by the starting of growth from latent buds 

 upon woody twigs, some of which were several years old. In some cases all 

 these methods of regeneration appeared on the same plant. 



Evaporation in its relation to the prairie problem, B. Shimek {Science, n. 

 ser., 33 (Hill), No. 8',0, p. ;9,?).— Attention is called to the fact that surfaces 

 exposed to the south and southwest in the Mississippi Valley are usually tree- 

 less and that where changes in to]K)graphy are abrupt the transition from forest 

 to prairie is likewise abrui)t. Field operations on the rate of evaporation on 

 treeless and forested areas have been made, and the results of these observations 

 show that evaporation increases with the temperature and the velocity of the 

 wind and that when the temperature is high the fluctuations in evaporation are 

 caused by changes in wind velocity. 



The bearing of these results upon prairie formation is discussed. 



An isolated prairie grove and its ecological significance, H. A. Gleason 

 (Science, n. ser., 33 {1011), Xo. SJ/O, p. l!),i). — A description is given of a 

 prairie grove in Champaign County, 111., abolit 1 by 3 miles in size, which is 

 located at some distance from a stream. The prevailing trees in the grove are 

 oaks, hickories, and black walnuts, with scattered individuals of other species. 

 The variation in the composition of the forest indicates that it migrated into 

 this region from the northeast. The grove is not continuous, but is broken by 

 areas of low ground which contain permanent standing water. 



It is concluded that formerly the whole moraine was covered with forest, but 

 that since the introduction of prairie fires all has been destroyed but this grove, 

 .jyhich is protected by standing water. The general conclusion is drawn that 

 forests were formerly of much wider extent in Illinois than at present, but 

 that the prairies do not owe their origin to prairie fires. 



Twin hybrids in (Enothera, with a suggestion concerning their explana- 

 tion, R. R. Gates {Science, n. ser., S3 {1911), No. 8^2, p. 262).— By means of a 

 large number of crosses the tyiie of behavior in Oenothera called by de Vries 

 twin hybrids has been confirmed, and many new crosses which had not pre- 

 viously been reported have been made. The author describes the results of a 

 number of cross pollinations and the forms pro<luced. and gives an account of 

 cultures from wild seeds, which indicate that there is a marked dimoiiihism of 

 some of the forms in the wild condition. This may account for the occurrence 

 of similar twin types in crosses in which CB. biennis is the female parent, the 

 condition being transmitted in the eggs, but not usually through the pollen. 



Cryptomeric inheritance of Onagra, C. S. Gageb {Science, n. ser., 33 {1911), 

 No. SJ/O, p. 191). — Attention is called to an abnormal plant of O. biennis that 

 appeared in a pedigreed culture following exposure to radium rays of the ovule 

 employed in producing the plant. 



The plant possessed two primary shoot systems of equivalent value but en- 

 tirely unlike in moiiihological characters. The effect was believed to be due to 

 the exposure to the radium rays, although this was not conclusively shown. 

 Hybrids produced between the two unlike halves manifested in the Fi and F2 

 generations the characters of only one of the parent shoots, and this is held to 

 indicate that the inheritance of a character and its expression are quite differ- 

 ent phenomena. 



Reversible sex mutants in Lychnis dioica, G. H. Shull {Science, n. ser.. 33 

 {1911), No. 840, p. 192). — The author describes the discovery in 1908 of hermaph- 



