280 
METHODS IN PLANT HISTOLOGY 
every preparation should contain transverse, longitudinal radial, and 
longitudinal tangential sections. 
The safranin and Delafield’s haematoxylin should show the bars 
of Sanio very clearly, as should also the safranin and crystal-violet. 
If a preparation shows the bars of Sanio and differentiates the torus 
of the bordered pit, the technic is good (Fig. 98). 
Jeffrey’s maceration method will isolate the tracheids and other 
cells, which can then be stained and mounted in balsam. Such 
preparations show features which might be overlooked in sections. 
The root .—The primary root should be studied in the embryo 
while it is still contained in the seed ; Collect material in September, 
October, or at any later date. If material is collected in winter, the 
seeds should be soaked in water for a day or two before fixing. In 
any case, remove the testa and cut a thin slab from opposite sides 
of the endosperm to facilitate fixing and infiltration. For secondary 
roots and also for the structure of the stele in the primary root, 
germinate the seeds and fix material after the hypocotyl has reached 
a length of 3 or 4 cm. The seeds of Pinus edulis, commonly called 
Pinon, or edible pine, can be obtained in most cities. They are 
particularly good for a study of the mature embryo and the seedling. 
The older roots are treated like the stems. The structure of roots 
2 or 3 mm. in diameter is wonderfully regular (Fig. 99). 
The leaves .—The leaves of our common gymnosperms cut readily 
in paraffin while they are young and tender, but as they approach 
maturity it is a fuitless task to attempt paraffin sections. 
Good sections may be obtained in great quantities with little 
trouble by the following method: Make a bunch of the needles as 
large as one’s little finger, wrap them firmly together with a string, 
allowing about i inch of the bunch to project above the wrapping; 
dip two or three times into melted paraffin; and then dip into cold 
water to harden the paraffin. While there is no infiltration, the paraf¬ 
fin holds the needles in place for cutting. Fasten in a sliding micro¬ 
tome and cut with the knife placed obliquely. Place the sections 
in water as they are cut and the paraffin can be easily skimmed away. 
Then fix the sections in 95 per cent alcohol for half an hour; transfer 
to 70 per cent alcohol, where they should remain for about 5 minutes; 
then to 50 per cent alcohol, where they should be kept until the 
green color, due to chlorophyll, disappears. Stain in safranin and 
light green. 
