11() THE AMERICAN MONTHLY [April, 



e developed under normal conditions. The measurements in- 

 cluding such variations areas follows: Hyphai 50-150 x 4-5 ; 

 conidia 50-280x4-5. The figures are all drawn to the same 

 scale, using compensation ocular No. 6 and objective 4mm. 

 Zeiss, with aid of camera lucida. The micrometer scale of this 

 combination is also projected by the side of the figure. 



This disease can be held in check by the use of the standard 

 carbonate of copper and ammonia mixture applied with a knapsack 

 sprayer. 



DIATOMS. 



Culture of Diatoms. — Dr. P. Miquel states that a very 

 favorable medium for the artificial culture of fresh-water diatoms 

 is ordinary fresh water in which have been thrown stems of 

 grasses, the cortical substance of grains of wheat, barley, or oats, 

 fragments of ]Muscinece,etc. ; soluble carbohydrates, albuminoids, 

 etc., have rather an injurious efl'ect than a favorable influence. 

 The presence of a very small proportion — from i to 5 per mil. — 

 of certain salts, such as those of soda, potash, or lime in the 

 condition of chlorides, bromides, iodides, phosphates, and sul- 

 phates, has a marked favorable effect on the multiplication of dia- 

 toms ; but they appear to prefer to obtain their silica from that 

 set at liberty by the decomposition of plants rather than from 

 soluble silicates. The marine kinds are easily cultivated in arti- 

 ficial sea-water, especiallv if containing fragments of Fiiais or 

 other sea-weeds. 



In another paper on the same subject published in Le Diatomiste^ 

 1893, the same author gives full instructions as to the best mode 

 of cultivating diatoms, both fresh-water and marine, the best 

 media for their growth, the most favorable temperature, light, 

 etc. The most destructive enemies to the diatoms are bacteria. 

 An apparatus is described for their culture free of bacteria. — 

 your. Royal ]\Iicr. Soc, Feb.^ -iSgj. 



Cultivation of Diatoms. — Dr. L Macchiati,in a preliminary 

 communication to the Journ. de jMicrographie., xvi, 1802, 

 points out that diatoms are easily cultivated in the nutritive solu- 

 tions used in vegetable physiology, provided that a few drops of 

 silicate of potash be added to the medium. Or the very water 

 which the diatoms inhabit may be used. This, when filtered, 

 and with the addition of a few drops of strong silicate of potash 

 solution, forms an excellent fluid. The medium, placed in a 

 watch-glass, is then inoculated with a loopful of the water inhab- 

 ited by the diatoms, and the two fluids having been thoroughh^ 

 mixed together by stirring, a loopful of the mixture is placed on 

 the surface of a cover-glass ; the exact thickness is previously 

 ascertained. To the margin of a cavity of a hollow-ground slide 

 is then applied some vaselin, and this is carefully placed over the 



