1894 THE MICROSCOPE. 61 



a glass slip with a concave centre. Examine with a low power. 

 If the find is rich, lay on a cover and examine the moss and 

 contained water with a 1 inch objective. See A. M. M. J., vol. 

 X, page 151, for an article on amoeba. 



PRACTICAL SUGGESTIONS. 



By L. A. WILLSON, 



CLEVELAND, OHIO. 



Metallic Crystals. — Crystals prepared in the following man- 

 ner are brilliant and gorgeous opaque objects. The Copper is 

 the most beautiful. They are easil}^ produced and no micro- 

 scopist should be without a few of these slides, especially when 

 he desires to excite the unfeigned admiration of his friends. 



Place on a cover a solution ot the chloride of tin, silver, gold, 

 platinum, copper or lead. The tin crystals will be precipitated 

 by placing a little pencil of cadmium on a cover with the solu- 

 tion. Silver maj^ be thus precipitated from the nitrate with ar- 

 senic, antimony, zinc, lead, iron or copper. Copper from the 

 chloride with bismuth, zinc, lead, tin or iron. 



Gold from the chloride with all those mentioned for silver. 

 The precipitating metal must be a little metallic bar laid on the 

 cover containing the proper solution. Mount in balsam, 

 between two covers, then cement on a bed of asphalt and ring 

 with shellac to prevent the asphalt from running in, and after 

 drying finish with asphalt. 



Pollen Tubes. — Claytonia Virginica or Spring Beauty, now 

 in blossom in the woods, furnishes an easy specimen for the ex- 

 hibition of pollen tubes. In order to see them, sever the style 

 and view the three stigmas. The tubes will be visible in the 

 grain adhering to the stigma. To see them a quarter inch ob- 

 jective will be the most serviceable. All the great works on bot- 

 any assert that to accomplish fertilization the pollen tube de- 

 scends into the ovary and comes into actual contact withth e 

 micropyle of the ovule. A few skeptics have doubted the as- 

 sertion whereat the authorities became wroth and declare that 

 non-experts cannot see or know anything about the matter and 

 nothing but highly expert manipulation can demonstrate the 

 truth. In Claytonia the tube is very distinct and to che non- 

 expert it looks equally as plain that the tube does not descend 



