748 



SCIENCE 



[N. S. Vol. XXV. No. 645 



the method of great use in sectioning rust 

 pustules, from both fresh and dried material. 

 It is also of very great value in the study of 

 hard seeds, such as the grains of cereals. 

 The paraffine method, at least as usually prac- 

 tised, is not successful in producing sections 

 of the starchy grains of cereals. Dr. A. 

 Mann, of the Department of Agriculture, 

 however, informs me that he has succeeded by 

 very long infiltration of both xylol and of 

 paraffine in obtaining very satisfactory sec- 

 tions of mature barley grains. By the freez- 

 ing method excellent thin sections of vrhole 

 grains (even of large corn) can be cut ■with- 

 out difficulty. On the other hand, the method 

 is very useful in cutting hard materials, as 

 small blocks of wood (soaked in water) grass 

 stems, etc. This is made possible by the 

 firmness of the mount, and by the direct and 

 unswerving approach of the knife, which 

 avoids the turning action of the blade, so 

 common in the cutting of free-hand sections 

 from such material. In dealing with such 

 material, moreover, by the paraffine method, 

 dehydration makes the wood so hard that th« 

 knife is very easily ruined. In the freezing 

 method, the blocks, on account of their water- 

 soaked condition, are less apt to injure the 

 knife. Again, large soft berries, as cran- 

 berries, are easily sectioned whole, and for 

 rapid sectioning of leaves the method is par- 

 ticularly useful. Osterhout's work (I. c.) 

 has demonstrated its usefulness in the treat- 

 ment of red sea-weeds. The method is thus 

 seen to have a wide range of usefulness. 



The freezing microtome method should find 

 a place in every botanical laboratory, first as 

 a supplementary aid to the paraffine method, 

 and second, as a quick method of securing 

 sections for ordinary morphological and an- 

 atomical work. It sometimes happens that 

 an instructor can obtain only a small amount 

 of material, which may be extremely rare, and 

 by this method he can usually obtain enough 

 excellent sections for a large class in a very 

 short space of time, without the delay neces- 

 sary for paraffine work, and without the waste 

 of material which is sure to attend the work 

 of sectioning when done by the students. 

 Again, in elementary classes, microtome work 



of a difficult nature is sometimes necessary, 

 and the students may be unable to obtain 

 satisfactory free-hand sections. In myco- 

 logical and pathological laboratories the 

 method is extremely useful. It has, more- 

 over, been found of very practical value in 

 medical pathological laboratories, where it is 

 used in rapid histological work. 



Perhaps the greatest general good could be 

 derived from its use in high schools, normal 

 schools and smaller colleges, for which the 

 apparatus for the paraffine method is too ex- 

 pensive, where the time is insufficient, and tha 

 courses necessarily too elementary to include 

 the study of the paraffine method. It is 

 especially to workers in these institutions that 

 I wish to direct attention to this freezing 

 microtome technique. The method should 

 prove of immense value in such institutions 

 on account of its cheapness, speed and general 

 usefulness. Hundreds of excellent sections 

 can be cut in a very short time and the 

 apparatus is always ready for use. An effi- 

 cient apparatus such as that shown in the 

 figure, can be obtained for $16 (duty free). 

 It is sold by J. Swift & Son, No. 81 Totten- 

 ham Court Road, London. 



The apparatus is shown in the accompany- 

 ing figure. The material to be cut is first 

 placed in a ten per cent, gum-arabic solution. 

 It may be soaked in this for one to twenty- 

 four hours, according to the size of the ma- 

 terial. It can, when necessary, be kept in the 

 gum arable for only a few minutes or even a 

 few seconds, though the longer soaking will 



