86 



EXPLANATION OF PLATE I 



Beginning at the top and following down to the bottom the grains are 

 named and their diameters given in microns. 

 Top, left — Timothy, Phleum pratense L., 28.5 

 Top, center — Plantain, Plantago lanceolata L., 30 

 Top, right — Birch, Betula alba L., 26, polar view, drawn as if partly cut away 



to show optical section 

 Second, left — Oak, Quercus alba L., 34.2, polar view 

 Second, right — Dandelion, Taraxacum officinale Weber, 34.2, polar view 

 Third, left — Carpet weed, Mollugo verticillata L., 32.3, showing four, and the 



ends of four more, of its twelve furrows 

 Third, right — Goldenrod, Solidago speciosa Nutt., 22 

 Bottom, left — Portulaca, Portulaca grandiflora Hook., 80.6 

 Bottom, right— Russian thistle, Salsola Pestifer A. Nels., 27.5 



