398 BOTANICAL GAZETTE [MAY 
of paraffin, corked, and set aside and not disturbed until the satura- 
tion point is reached. The container is next placed on the oven 
until the new saturation point is reached, next in the oven, and 
imbedding is proceeded with in the usual manner. Even here, when 
dealing with delicate plants, the xylol-paraffin is poured off only 
to the wire gauze and the container again filled with blocks of 
paraffin. 
By this method paraffin is slowly dissolved, and as it descends is 
slowly and uniformly diffused through the xylol, thus preventing, 
in a large measure, damage to the object by rapid changes in density. 
It takes longer to reach the saturation point than when solid par- 
affin is permitted to fall to the bottom of the container, but little 
plasmolysis results. 
Using delicate liverworts for test objects it was found that no 
deformation of tissue took place, except that which can be accounted 
for by the excessively large coefficient of expansion (o0.00027854) of 
paraffin. The deformation caused by paraffin in an artificial cell 
was found to be exactly the same as is always present in plant cells 
when the paraffin is quickly cooled. 
Many workers use a very close series of alcohols in dehydrating 
and a similarly close series in replacing alcohol with the paraffin 
solvent, and then undo all their careful work by indiscriminately 
adding paraffin to the solvent. 
A method of fixing paraffin ribbons to the side with certainty 
Albumen fixative, which is almost universally used to fasten 
paraffin ribbons to the slide, has many excellences and a few disad- 
vantages. Among the latter is the property of coagulating when 
subjected to moderate heat, and in consequence losing its adhesive 
quality. Because of this it is sometimes impossible to use sufficient 
heat to straighten refractory or much wrinkled ribbons, especially 
if paraffin melting at 58—60° is used. Again, it is almost impossible 
to fix sections of certain refractory plants to the slide, even if the 
ribbons are first straightened by floating on warm water and then 
transferred to an albumen coated slide and allowed to dry without 
heating. This is particularly true of sections of antheridial and 
archegonial heads of some mosses and of the strobili of Selaginella. 
