Miocene 



A geological epoch which began about 28 million years 

 ago and lasted about 16 million years, in the Tertiary pe- 

 riod of the Cenozoic era. 



Mississippian Period 



A geological period in the Paleozoic era (q. v.), which 

 began about 280 million years ago and lasted for about 25 

 million years. 



Mistral 



A cold, northerly wind along the northwest Mediter- 

 ranean coast, especially during winter. 



Mite 



An animal in the order Ac&rina, class Arachnida, phylum 

 Arthropoda; including both free-living and parasitic forms. 



Mitochondrion 



A minute body in the cytoplasm in cells, the chief loca- 

 tion of respiratory enzymes, syn. Chondriosome. 



Mitosis 



The ordinary division of a nucleus that includes the 

 longitudinal doubling of chromosomes to form pairs of 

 chromatids, separation of each pair to form two daughter 

 nuclei; so a constant number of chromosomes is maintained. 



Mitotic 



Refers to Mitosis. 



Mixed Forest 



A forest composed of trees of two or more species, usu- 

 ally at least 20 per cent of the trees are of other than the 

 leading species. 



Mixed Prairie 



An extensive grassland type lying west of the tall-grass or 

 True prairie in North America, consisting of a mixture of 

 tall-, short-, and midgrasses, and other herbaceous plants. 



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