EXPLABTATION- OF PLAIES. 135 



vulgaris. The two former show crenate margins, reticulated 

 surfaces with polygonal dotted areas and ramparts exquisitely 

 beaded, whilst the last adds a velvet pile as fringe to each ram- 

 part, at the same time cheveux-de-fris and veil. Undoubtedly 

 the Thrift stands queen among the pitted pollen grains. 



As examples of pollen presenting exquisitely carved facets, 

 Urtica dioica, Plantago lanceolata, Dianthus caryophyllus and D. 

 harhatus, Stellaria nemorum and S. media., are hard to beat. All 

 show beautifully sculptured geometrical surfaces, but the first 

 adds a circular central boss to each facet, and the last also a 

 delicate fringe. Facets and polygonal form are as characteristic 

 of Caryophyllacem as are oval form and large walled pits of 

 Liliacece. 



As regards the bearing of this study on classification, I will 

 only say that, so far as the evidence of pollen alone is concerned, 

 it is not easy to see why PoUanthus tuherosa is grouped with the 

 Liliacece, Tropceoleum Canariensis with the Geraniacece, Clematis 

 tubulosa with the Ranunculace^, etc., but on this matter more 

 may be said another day. 



EXPLANATION OF PLATE IV. 



POLLEN-GEAINS. 



No. 



1. Ilex Aquifolium — trefoil grain. 



2. Geranium pusillum — notched grain. 



3. Euphorbia splendens — trefoil grain. 



4. Bryonia dioica — trefoil grains, numerous. 



5. Oncidium variecorum — two pollinia. 



6. Orchis mascula — pollinia. 



7. Hahenaria hifolia — pollinia. 



8. Orchis maculata — pollinia. 



9. Dendrohium nohile — pollinia. 



10. Melampyrum pratense — scatterers. 



11. Ruhus ceesius. 



12. Potentilla anserina — grains, two sizes. 



