82 KANSAS Academy of Science. 



staining. I have observed thirty or forty diatoms of one variety adhering to- 

 gether by means of this covering, sometimes in a solid phalanx, and again drawn 

 out in a line, until the tips only, of the frustules, overlap. 



Let us return, for a moment, to the process of division. That agamic biparti- 

 tion cannot continue indefinitely without senile degeneration is evident; and the 

 first sign of degeneration is reduction in size. By division the cell contents first 

 separate, and then the two valves; two new valves of silica having been secreted. 

 Hence, each of the two new individuals is again incased within a silicious shell 

 composed of half of the old frustule and half of the new. It is evident that the new 

 plant, possessing the lid for its outer covering, would be larger than the one in- 

 cased within the box. Hence, let me say again, that size cannot be a very impor- 

 tant factor in determining a variety. 



The process of division continues with wonderful rapidity. Prof. H. L. Smith 

 says: "I have been unable to ascertain the time occupied in a single act of division, 

 but, supposing it to be completed in twenty-four hours, we should have as the 

 progeny of a single frustule the amazing number of 1,000,000,000 in a single month." 

 Others claim that the division is completed in three and six hours. 



My purpose, however, is not to consider methods of reproduction, but to tell 

 you, from my limited experience, what methods I have found most convenient for 

 collecting, cleaning and mounting our Kansas varieties. 



Light and moisture alone are necessary for the development of diatoms; hence, 

 they may be found in running or standing water, but never in putrid water. In case 

 the growth is luxurious, they will be found as a greenish-brown layer upon sub- 

 merged stems and leaves of plants, upon rocks, or the surface of mud. In Kansas 

 they are usually found upon the surface of the mud — our streams have usually mud 

 bottoms. By means of a shallow dipper or long-handled spoon, the collector may 

 obtain a quantity of this slime, mixed with earth. The fluid thus collected should 

 be well shaken and poured into a flat dish, where it is allowed to settle for several 

 hours. The heavy earthy particles will sink to the bottom of the dish, while the 

 surface will be covered with a thick brownish coating. All the supernatent water 

 should be poured off gently, or, better, carefully removed with a small pipette. 

 Gently touch the dry finger to the green covering and wash off the adhering particles 

 into a small vial. If care is taken that the touch be light, diatoms almost entirely 

 free from foreign matter may be obtained. I have frequently tried the well-known 

 process of gigging, but have invariably failed to obtain pure diatoms, since our fine 

 clay will be held in suspension as readily as will the light diatoms. Moreover, the 

 clay of Douglas county contains so much silica, that, once mixed with the cleaned 

 diatoms, it is almost impossible to extricate them from the white, clinging, flocculent 

 mass. Any chemical which will destroy the flocculent silica will also attack the 

 frustules. 



The pure diatoms, once obtained within the vial, may be cleaned — or, in other 

 words, freed from their cell contents — in various ways. A very common and useful 

 method is to boil them in acid — sulphuric, nitric, or hydrochloric. I usually boil 

 them in concentrated sulphuric acid, and destroy the carbon thus formed with nitric 

 acid. A test tube will be found a very convenient receptacle during boiling. Allow 

 the liquid to cool, and, after a few hours, the diatoms will have settled to the bottom 

 of the tube. Pour off the supernatent acid and fill the tube with pure cistern water, 

 or, better still, distilled water. Again allow the contents to settle, and pour off the 

 water. Repeat this process until all traces of the acid have been removed. Be not 

 discouraged if it is necessary to repeat this process twenty or thirty times. Once 

 freed from the acid, the beautiful white frustules are ready for mounting. 



Dry upon a slide or cover-glass a drop of the pure water containing them. Care 



