Journal of Applied Microscopy. 325 



inferior to the root-tips of the common Podophyllum or May-apple. In this 

 plant the chromosomes are very large and in sections stand out like ropes, the 

 mitotic figures are abundant in the growing root-tips, and the material is easily 

 obtained. 



An object so exceedingly favorable for the purpose deserves to be generally 

 used by teachers of biology, though, so far as I am aware, it is almost- unknown 

 among the zoologists. It was recommended to me by Professor D. T. Mac- 

 Doiigall, and has done such excellent service in my classes that I believe other 

 biologists will find it a welcome addition to their list of available class material. 



The following simple method of preparation has given satisfactory results in 

 my experience : the root-tops, freshly pulled from the moss in which they were 

 growing, were cut off and dropped at once into Hermann's fluid. After washing 

 and dehydrating they were stained /// toto in Kleinenberg's htematoxylin and 

 embedded in paraffine for sectioning. Sections about 1 fx thick, cut parallel with 

 the long axis of the rootlet, are most satisfactory. Thinner sections than these 

 do not show entire mitotic figures. Under a Bausch & Lomb i-inch or a Leitz 

 No. 7 objective, spirem stages, chromosomes, and achromatic spindles may be 

 made out with a clearness equaled by few objects under a yL-inch oil-immersion. 



W. S. NiCKERSON. 

 Laboratory of Histology and Embryology, University of Minnesota. 



Collodion Sectioning of Golgi Preparations. 



In cutting sections of nervous tissue impregnated by the Cox-Golgi method, 

 I have adopted a method which I have never seen described, but which may be 

 employed by others. After the tissue has been impregnated in the usual manner, 

 it is rinsed off with water, and is then placed for not over half an hour in each 

 95 per cent, and absolute alcohols, and for the same length of time in a mixture 

 of equal parts of absolute alcohol and ether. Next comes immersion, for say 

 twenty minutes, in thin and then in thick collodion, and then it is imbedded as 

 usual. So far the process is the usual one. To harden the collodion I employ 

 chloroform instead of weaker grades of alcohol, not only on account of its more 

 rapid action, but because its effects are less injurious. As soon as the collodion 

 has become somewhat firm, the paper employed in imbedding is removed and 

 the block is placed in a mixture of one part carbolic acid and three parts xylol. 

 In this it can be kept for weeks in a good condition. Indeed I have cut sections 

 which showed fairly good pictures after a stay in the xylol-carbolic mixture of 

 two years. The sections are cut with a razor flooded with the xylol-carbolic 

 fluid, and are at once transferred to the slides and mounted directly in balsam. 

 This method, as will be seen, has several advantages ; its greatest drawback is 

 the disagreeable effect of the carbolic acid, which is almost certain to get on the 

 hands, no matter how carefully one may try to avoid it. I may say, in closing, 

 that I use photographers' gun cotton instead of celloidin in making my collodion. 

 I think it works better ; it is certainly much cheaper. 



J. S. KiNGSLEY. 

 Tufts College. 



