Spermatophytes Gymnosperms 



245 



fixing. Even transverse sections are not difficult to cut while 

 fresh (Fig. 84). A piece of cycad trunk 15 to 30cm. in diameter 

 and 20 cm. in length will survive a journey of six weeks or even 

 two months, if care be taken to coat the exposed ends with a mixture 

 of melted paraffin and moth balls, using three or four 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. 84. Dioon spinulosum: photomicrograph of transverse section of wood of 

 Dioon spinulosum, cut from fresh material. X105. 



The course of the vascular bundles, as they pass to the cones, is 

 quite peculiar. Instructive preparations may be made by cutting 

 longitudinal sections, about 3 mm. thick, through the apex of the 

 stem and, without staining, clearing thoroughly and mounting in 

 balsam. In this way we have mounted sections 5 cm. long, 15 cm. 

 wide, and 3 mm. thick. 



The root. Small roots, up to a centimeter in diameter, are easily 

 cut freehand. The tender root-tips and also the peculiar " root- 

 tubercles " should be fixed in chromo-acetic acid and imbedded in 

 paraffin. 



