T.S. Lily bud 



NITROCELLULOSE SECTIONS 



149 



adhesion. Another useful method of han- 

 dhng large numbers of celloidin sUdes is 

 that of Linstaedt 1912, also described in 

 Chapter 28, V 21.2. The method there 

 given can be followed; it results, in effect, 

 in the fusing of a large quantity of cel- 

 loidin sections into a single sheet of 

 celluloid, which may then be handled 

 through stains, etc. as if it were a simple 



section. It will be noticed that the sheet 

 itself is made of celluloid — not celloidin— 

 which is a material which does not readily 

 pick up stains. The two methods of Lon- 

 geron involve the removal of the celloidin 

 after the sections have been mounted, and 

 leaves one to wonder why (celloidin should 

 have been used, instead of paraffin, in the 

 first place. 



Typical Example 



Preparation of a Transverse Section of a Lily Bud 



It has already been pointed out that 

 one of the best uses to which celloidin maj^ 

 be put is the preparation of sections of fine 

 structures containing cavities which would 

 not be held b}' paraffin. The example here 

 selected is a case in point, for it would be 

 almost impossible by the ordinary paraffin 

 section technique to take a transverse 

 section of a large flower and to maintain 

 all the different parts in relation to each 

 other. It would indeed be almost impos- 

 sible to secure a section at all without 

 gross collapse of the parts. 



The bud of a lily has been selected be- 

 cause it is such admirable teaching mate- 

 rial. Sections may be taken through a 

 level which will show both the stamen and 

 the pistil, and the material is sufficiently 

 large to permit an elementary botany 

 class to get a clear idea of the arrangement 

 of the different parts with the use of mag- 

 nifications no higher than those provided 

 by a hand lens. The method of staining 

 selected, however, is sufficienth^ good to 

 permit the examination of the individual 

 parts, bj- an advanced class, under the 

 high power of the microscope. 



The exact species of hly, provided it is 

 one of the trumpet varieties known to 

 florists, is quite immaterial, and the bud 

 should be taken about a week before it 

 is open. The best fixative to use for this 

 kind of thing is one of the chromic- 

 formaldehyde-acetic mixtures known to 

 botanists under the general term of C RAF. 

 Several formulas for these mixtures are 

 given in Chapter 18 under the heading 

 F 6000.1010; the ffiiids of Navashin 1912, 

 Belling 1930, and Randolph 1935 are the 

 ones widely used by botanists. It makes 

 little difference which of these formulas 



is employed, but they must be made up 

 immediately before use to prevent the 

 reduction of the chromic acid by the 

 formaldehyde. 



A hly bud ly/' long X }i" in diameter 

 will need to be fixed for about four days 

 in one of these fluids, which should be 

 changed daily and kept in the dark. As 

 soon as the bud is cut from the plant it 

 should be immersed in the fixative and the 

 extreme tip cut off to permit the contained 

 air to leave. After fixation in these fluids, 

 the bud should be washed for 24 hours 

 in running water and then transferred 

 through 20%, 50%, 70% and 90% alcohol 

 (about a daj- or two in each) to 95% alco- 

 hol, which should be changed as often as 

 it becomes discolored. It is necessary to 

 remove the chlorophyll, or else this will 

 subsequently diffuse into the celloidin, 

 from which it is almost impossible to re- 

 move it. If the process of decolorization in 

 95 % alcohol is too slow for the worker, he 

 may transfer the bud to absolute alcohol 

 until it is dehydrated, and then to chloro- 

 form where the remaining chlorophyll will 

 be extracted very rapidly. The risk in this 

 procedure, however, is that the chloroform 

 will not subsequently be sufficiently re- 

 moved, and will thus prevent proper infil- 

 tration by the celloidin. If chloroform is 

 used, the bud must be removed as soon as 

 bleached to absolute alcohol, which is 

 changed as often as the least smell of 

 chloroform remains. It is then put through 

 at least 6 changes of 95 % alcohol, with one 

 day in each, before being transferred to 

 fresh absolute alcohol to complete the 

 dehydration. 



The writer's preferred method of dehy- 

 dration for large objects has already been 



