11« THE AMKIilCAN .MoNTlllA [April, 



r* developed under normal conditions. I'lie meaMiienunts in- 

 cluding such variations areas follows: 1 1\ plui' ^o-i ^o x 4-j; ; 

 conidia 50-^80x4-5. The figures are all drawn to the same 

 scale, usin«; compensation ocular No. 6 and ohiective -|mm. 

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

 combination is also projected In the side of the fijjjure. 



This liisease can he heUI in check hy the use of the sl;inilard 

 carhonateof copperand ammonia mixture applied with a knapsack 



DIATOMS. 



Culture of Diatoms. — Dr. 1*. Mi(piel states that a very 

 favorable mediuu) tor the artificial culture of fresh-water diatoms 

 is ordinary fresh water in which have been thrown stems of 

 jjrasses, the cortical substance of «;rains of wheat, barley, or oats, 

 trajjmentsof Muscine;e,etc. ; soluble carbohydrates, albuminoids, 

 etc., have rather an injurious efVect than a favorable influence. 

 The presence of a very small proportion — from 1 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 eflect on the multijjlication 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 containinjj tiagments of I^^ucus or 

 other sea-weeds. 



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

 1892. 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. I\oval Mirr. Soc, Feb., j8qJ. 



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

 communication to the yourti. de Micrographic, xvi, 1802, 

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

 tions used in vegetable physiologv. provided that a few drops of 

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

 which the diatoms inliabit 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 

 v\'atch-glass. is then inoculated with a loopful of the water inhab- 

 ited bv the diatoms, and the two fluids having been thoroughly 

 mixed together Vn' 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 



