374 G. ERDTMAN 



appearing in enormous quantities after having been more or less hidden for 

 ages? Did they invade new territories, suppressing the old vegetation? Did 

 they leave the soil, estabhshing themselves as "preloranthaceous" parasites, 

 eventually killing the Gymnosperms or other plants upon which they lived? 

 What is ''Micropinus'" of which small pinoid pollen grains are encountered in 

 old Icelandic strata? Have they any connection with the small pollen grains 

 in the recently described coniferous genus Cathaya from China (cf. PI. VI)? 

 What about the possibility of picking out fossil birch pollen grains, etc., 

 from Icelandic Interglacial and Post-glacial deposits, and having them sub- 

 jected to study under the electron microscope? Replicas showing the fine 

 details of the exine relief can, with some training, be made without too great 

 difficulty, as shown by M. Takeoka (unpubl.). Replicas of a number of 

 pre-Quaternary pollen grains and spores have been made at the Palynological 

 Laboratory, Solna. This would mean another approach to the study of 

 stability and instability, in the course of the ages, of certain characteristics in 

 special plants. Which species are static, or which are in statu nascendi? 

 What is, in evolution, the real importance of apocracy versus statocracy? 



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