CRETACEOUS CONITERALES 9 
good specimens. It was also found advantageous to first screen off 
the coarser fragments by means of a quarter-inch mesh, thus facili- 
tating the subsequent examination of the finer material for valuable 
fragments, as the larger pieces are seldom well preserved and there- 
for merely serve to obscure those of greater value. 
The critical examination of the material was carried on by means 
of the dissection microscope and a lens of two- or three-inch focus. 
Such a lens has a large field and magnifies sufficiently to enable all 
the fragments of value to be readily picked out. The material thus 
selected has, of course, to be sectioned for the study of any internal 
details of diagnostic value, and, as a preliminary step, mineral 
matter is removed by treatment with a rather strong solution of hydro- 
fuoric acid. This serves to eliminate everything but iron pyrites, 
which has to be accepted as a necessary evil, since any reagent which 
will effect its removal also destroys the material. However, it is 
possible in most cases, on account of the relative abundance of the 
specimens yielded by the process of maceration described above, to 
select those fragments which are free from pyrites for subsequent 
examination. After treatment with hydrofluoric acid for two or 
three days, the material, after careful washing and dehydration, is 
transferred to successively thicker solutions of celloidin in synthol- 
ether, equal parts. The celloidin containing the objects is finally 
thickened up by the addition of chips of celloidin, until it will no 
longer run in the cold. The entire process of embedding is carried 
on in a paraffine bath, at a temperature of about 60° Centigrade, 
in wired bottles. When the celloidin has been sufficiently thickened 
the pieces of lignite are removed with forceps, care being taken to 
cool the bottle beforehand and to have the objects covered with a 
thick layer of celloidin. They are then plunged into chloroform, 
where they remain several hours until the celloidin has become 
thoroughly hardened. Finally they are transferred to a mixture of 
equal parts of 90 per cent. alcohol and glycerine, where they may be 
kept indefinitely. 
When the objects are to be cut, ios are attached to the object- 
carrier of the sliding microtome (Jung-Thoma), having previously 
been cemented to blocks of wood by means of thin celloidin, which is 
allowed to dry hard. 
Material prepared by the above method furnishes thin and satis- 
factory sections, which are well suited for photomicrographic pur- 
