137 



HANGING LENGTH OF TAPE 

 WITH C-ELATINE CAPSULES. 



Fig. 255. Polymerization of the methacrylate with UV light. 



tioned, to over-heating during the initial stages of polymerization, or to 

 an over-concentration of pollen grains, or insufficient washings of the 

 pollen material with methacrylate. A capsule with air-bubbles can, never- 

 theless, be used for cutting if the pyramid (see below) is made either at 

 the side of the bubble or just above it. 



The cutting, oj the pyramid 



After soaking in water the gelatine capsules can be easily removed from 

 the plastic units which, when dry, are ready for cutting. A unit is fixed 

 in a steel object-holder (made by LKB-Pnxkd^ter, Stockholm 12) in such 

 a way that three to four millimetres of the pollen-bearing part protrude 

 from its mouth (Fig. 256). After trimming the top of the plastic unit with 

 a razor blade (Fig. 257), a thin foursidcd process, the pyramid, containing 

 the pollen grains or spores for sectioning is carved from the apex. 



