July, 25, 1913] 



SCIENCE 



133 



While Degative phototropism in Diaptomus can 

 be reversed by acids, positive phototropism 

 brought about by chemical means can not be re- 

 versed by strychnin (atropin or caffein)." 



A. E. Moore 

 The Universitt or Calipobnia, 

 July 8, 1913 



THE POWDERY SCAB OF POTATO (SPONGOSPORA 

 SOLANi) IN MAINE 



The potato tuber scab caused by Sportgo- 

 spora Solani (Brunch) has been known in 

 Europe since 1842. It was recently reported 

 from Canada by Giissow,' but has hitherto not 

 been found in the United States. That it 

 would become established here has been feared 

 by those acquainted with the serious injuries 

 it causes in Great Britain, whence heavy 

 importations of potatoes were made in 1911 

 and previous years, to supply American 

 markets. 



The writer discovered this disease on June 

 23 in potatoes just brought to Houlton from 

 Presque Isle, Aroostook County, Maine. 

 There is no probability as yet that a large 

 amount of Spongospora exists there, but 84 

 diseased tubers were sorted out of four barrels, 

 which represented a lot of 500 barrels. 



The milder forms of powdery scab resemble 

 the common Oospora scab. The pustules are 

 at first closed, but later break out into large 

 open sori. Twenty-six of the tubers collected 

 showed this form. 



The source of the disease is not known. 

 The original infection may have been brought 

 from Europe before the Plant Quarantine Act 

 went into efiect or seed potatoes bearing the 

 disease may have come from the adjacent 

 province of New Brunswick, in Canada, where 

 powdery scab already occurs. 



It is hoped that pathologists all over the 

 country will now watch for this disease and 

 that every eifort be made to stamp it out. 

 I. E. Melhus 



Bureau op Plant Industry, 



V. S. Department or Agriculture, 

 Houlton, Maine 



'Moore, A. E., loc. eit. 



' Phytopathology, Tebruaxy, 1913, p. 18. 



A NEW section SOUTH FROM DES MOINES, IOWA 



The grading of a new railroad line from 

 Des Moines to Allerton, passing from Polk 

 County through Warren, Marion and Lucas 

 into Wayne County, affords an excellent series 

 of exposures such as have never before been 

 available in this region. The relation which 

 this series makes evident assists in the inter- 

 pretation of observations already recorded, and 

 the section itself serves as a standard with 

 which to compare work yet to be accomplished 

 in south central Iowa and adjacent Missouri. 

 The general relation will be of interest to all 

 who keep informed on the Pleistocene work of 

 the country. 



The Loess 



The best exposure of loess that the writer 

 has seen in this portion of the state is south of 

 Des Moines, half a mile north of Coon Valley. 

 Here twelve to fifteen feet of grayish yellow 

 porous loess with faint horizontal lamination 

 may be seen capping the bluff for a quarter 

 of a mile. At the two ends of the cut the 

 loess is exceedingly fossiliferous, and charged 

 with concretions. In the hills east of Car- 

 lisle, even as far as Hartford, a distinct fos- 

 siliferous loess may be seen; but further south 

 it does not form a conspicuous deposit. On 

 the brow of hills away from the highest por- 

 tion of the upland it is not present at all. 



The " Gumbo " — The Loveland 

 Along the sides of all cuts through the up- 

 land may be seen a clay yellowish above, 

 bluish below, of a thickness varying from a 

 few feet up to perhaps twenty feet. It is 

 nearly free from pebbles, but here and there a 

 few scattered ones may be found that are haK 

 an inch in diameter, and very rarely one as 

 large as an inch. Two were recently found 

 as large as two inches in diameter. There are 

 found scattered through the clay grains chiefly 

 of granite about an eighth of an inch in 

 diameter. The clay is generally free from 

 distinct stratification, often silty in appear- 

 ance, and slumps badly throughout the entire 

 length of the railroad. In the upland where 

 thickest it is found on the bowlder and pebble- 

 bearing portion of the Kansan drift with no. 



