852 



SCIENCE. 



[N. S. Vol. XII. No. 309. 



February, 1897, there occurred a long spell of 

 hot weather, lasting from the 7th to the 18th 

 with maximum temperatures between 82.6° on 

 the 7th and 107.3° on the 10th, or over 100° on 

 five days and over 90° on ten consecutive days. 

 On the morning of February 8th the tempera- 

 ture at the Adelaide Observatory at three feet 

 below the surface was 71.5°; at five feet, 68.6°; 

 and at eight feet, 67.6°. On the morning of the 

 18th the readings were 73.6°; 69.3° and 68.4° 

 respectively, showing a gradual increase during 

 the intervening period, the increase being 2.1° 

 in the ten days at three feet, 0.7° at five feet 

 and 0.9° at eight feet. These observations 

 show clearly ' that it requires a very long con- 

 tinuance of heat to materially affect the ther- 

 mometers ten feet only below the surface.' 

 R. Dec. Waed. 



BOTANICAL NOTES- 



THE POWDERY MILDEWS. 



A NOTABLE contribution to the literature of 

 fungology has appeared in Mr. Ernest S. Sal- 

 mon's 'Monograph of the Erysiphacese,' pub- 

 lished as Volume XI. of the Memoirs of the 

 Torrey Botanical Club. It constitutes a thick 

 octavo pamphlet of nearly three hundred pages, 

 and nine plates of one hundred and seventy- 

 five figures. The paper opens with a couple of 

 pages of remarks on the. limits of the family, 

 eight or nine pages on morphologj' and life his- 

 tory, a few pages devoted to the history of the 

 study of the group, the connection between 

 host and parasite, and distribution of the spe- 

 cies. The family is restricted to the six genera 

 Sphaerotheca, Podosphaera, Uncinula, Micros- 

 phaera, ErysipheandPhyllaciinia. All the known 

 species in the world are included, and it speaks 

 well for the conservatism of the author that 

 although he examined the material in the most 

 important collections in Europe and America, 

 he has found it necessary to describe but two 

 new species and two new varieties. Such con- 

 servatism and self-denial are most commenda- 

 ble and encouraging, and may well serve as a 

 model for other monographers, who too often 

 find new species every time they turn over 

 their material. 



So conservative has been the writer of this 



monograph that under his treatment the grea 

 number of specific names in the family is re- 

 duced to but sixty species and varieties. Thus, 

 while Erysiphe has had one hundred and sixty- 

 five species and varietal names associated with 

 it, there are here but nine ; so the fifty-eight 

 names under Microsphaera, are reduced to nine- 

 teen ; the twenty-four under Podosphaera to five; 

 the twenty-one under Sphaerotheca to six ; the 

 thirty- eight under Uncinula, to twenty; and the 

 nine under Phyllaclinia, to one. Of course it is 

 not to be supposed that Mr. Salmon made all 

 these reductions ; to a large extent they had 

 been made already by other students of the 

 family, but it is greatly to his credit that with 

 such an opportunity he did not give us a greatly 

 increased list. 



According to this monograph the accepted 

 names of some of the more common of the 

 Powdery Mildews are as follows : Cherry Mil- 

 dew, Podosphaera oxycanthae ; Rose Mildew, 

 Sphaerotheca pannosa ; Gooseberry Mildew, 

 Sphaerotheca mors-iivse; Willow Mildew, Uncinula 

 salicis ; Grape Mildew, Uncinula necator ; Lilac 

 Mildew, Microsphasra alni ; Pea Mildew, Ery- 

 siphe polygoni; Sunflower Mildew, Erysiphe 

 cichoracearum. 



PLANT BREEDING. 



From a paper by H. J. Webber and E. A. 

 Bessey on ' The Progress of Plant Breeding in 

 the United States,' recently published in the 

 Year-book of the Department of Agriculture, 

 the scientific botanist may learn much which 

 may well surprise him as to what has been ac- 

 complished in the work of plant breeding. 

 That man can bring about definite results by 

 the careful breeding of animals is more or less 

 well known, but that plants may be bred with 

 as definite an object in view, and as successfully, 

 is not yet a matter of common knowledge. 



It is only during the latter half of the present 

 century that much progress has been made in 

 plant breeding proper, the earlier efforts at the 

 improvement of plants having been through the 

 selection of seeds of the most desirable plants 

 for further cultivation. Downing, Hovey, 

 Wilder and some other far-seeing horticulturists 

 of the earlier days continually urged the breed- 

 ing (' crossing ') of the better varieties of fruits 



