270 
METHODS IN PLANT HISTOLOGY 
They cut better while fresh; consequently, if one can get material, 
it is a good plan to send it to the laboratory and have it cut before 
fixing. Even transverse sections are not difficult to cut while 
fresh (Fig. 93). A piece of cycad trunk 15 to 30 cm. in diameter 
and 20 cm. in length will survive a journey of 6 weeks or even 2 
months, if care be taken to coat the exposed ends with a mixture 
of melted paraffin and moth balls, using 3 or 4 moth balls as large 
as marbles to half a kilo of paraffin. If material is to be fixed before 
cutting, use 6 to 10 per cent formalin in water. 
Fig. 93.— Dioon spinulosum: photomicrograph of transverse section of wood 
sum, cut from fresh material. X105. 
of Dioon spinulo- 
Dr. La Dema Mary Langdon succeeded in cutting paraffin sections 
of the adult wood of Dioon spinulosum. 1 She fixed 1 to 2 cm. cubes 
of adult wood in formalin-acetic acid-alcohol (6 c.c. formalin, 
3 c.c. acetic acid, 100 c.c. of 50 per cent alcohol). After thorough 
washing, 24 to 48 hours in running water, the blocks were softened for 
3 to 6 weeks in 50 per cent hydrofluoric acid in water. With dry 
material, the cubes were boiled and cooled repeatedly to remove air. 
The usual gradual processes of dehydrating, clearing, and infiltrating 
1 Botanical Gazette, 70:82-84, 1920. 
'•••Iff 
Mm 
