208 THE AMERICAN MONTHLY [September, 



BIOLOGICAL NOTES.* 



Mildew upon Cucumbers. — Prof. B. D. Halsted reports in the 

 Botanical Gazette finding a species of Peronospora upon tlie leaves of 

 cucumber vines bearing fruit. The species is not the same as that 

 found upon another species of cucurbitaccce. He suggests the import- 

 ance of being on the lookout for this destructive disease. JShould it be 

 found to attack squashes and melons as well, the danger would be more 

 serious. It may be hoped tliat since this species is not the same as is 

 found on Sicyos attgulattis the new species may not attack the other 

 cultivated cucurbitacejE. 



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Peculiar conjugation of Spirogyra. — Mr. C B.Atwell, of Evans- 

 ton, 111., in the same number, reports a peculiar phase of conjugation 

 of Spirogyra longata in which the protoplasm of one cell conjugates 

 with two adjacent cells of another filament, resulting in what he calls a 

 "• phase of polygamy." The zygospores thus formed are of unequal 

 size. The two cases of such conjugation figured are from two adjacent 

 cells of one filament with long cells to four adjacent cells of a filament 

 with much shorter cells. The conjugating processes from the two pairs 

 of short cells are in contiguous ends of cells. It is known that some 

 species of spirogyra occasionally show the conjugation of two adjacent 

 cells in the same filament. May not this be an instance bearing rela- 

 tion to ortlinary monoecious and the normal mode of conjugation.'' If 

 the two processes from adjacent cells had touched one another they 

 would perhaps have formed monoBcious union. This suggests the in- 

 teresting question which, so far as we know, has not yet been answered, 

 What determines the location of the conjugating cells .^ It is very rare 

 that a process does not find a mate to meet it. Such an instance as this 

 may indicate the fortuity of this meeting. 



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^A^ate^ Analysis. — Dr. Charles Smart, U. S. A., contributes to the 

 Sanitarian a valuable paper upon this subject, in which he treats in 

 his careful and able style the various problems which enter into any 

 really valuable test of water that is to be used for drinking purposes. 

 The discussion of the methods of determining the presence of albuminoid 

 matter, and particularly the determination of urea, is made practical 

 by the citation of instances in which the reliability of the residts is 

 proved in subsequent revelations of sewer contamination. The methods 

 of microscopical examination are also well represented and emphasized, 

 and the bearing of the presence of various forms of organic matter upon 

 the purity of the water is discussed. It seems to us, however, that Dr. 

 Smart has not stated the importance of this part of the analysis with 

 sufficient emphasis for the instruction of those who suppose that the 

 chemical tests are the more critical and important. For all questions 

 of general purity and ordinary contamination of drinking water we must 

 of course rely upon chemical analysis, but there are certainly instances 

 in which these tests reveal such slight impurities that the chemist would 

 not be warranted in pronouncing the water even dangerous when the 

 presence of small niniibers of disease germs, which only a careful ex- 



* This Department is conducted by Prof. J. H. Pillsbuky. 



