BEAL ON MICHIGAN FLORA. 5 



and H. C. Skeels of Grand Rapids; C. 1). McLoutli of Muskegon; G. H. 

 Hicks of Grayling, Owosso and the Agricultural College; C. K. Dodge 

 of Port Huron; George M. Bradford of Bay City; W. K. Brotherton of 

 Oakland; Geo. W. Davis of Tekonsha; J. \y. Stacy of Clarksville. Col- 

 lections have been received, by gift or purchase, from Prof. (.'. A. Davis 

 formerly of Alma, now of the University; of O. A. Farwell formerly of 

 Keweenaw county, of Ypsilanti, and later of Detroit; and Rev. Francis 

 Daniels formerly of Alto, Kent county, Manistee and Sturgis; W. S. 

 Cooper of Alma. 



After all has been said and done, the study of the flora of the state at 

 best can only be considered as fairly begun. By far the greater areas 

 have not yet been seen by any systematic botanist and very few regions 

 have been visited by one who is an expert in some one or more of the 

 more difficult families. 



What species nourished in large areas will never be fully known, since 

 man has cut off, burned over and plowed under tens of thousands of acres 

 of the virgin wilderness ! Swamps, marshes and lakes have been drained 

 and the land occupied by farm crops. Many native plants are rapidly 

 shifting from one place to another. 



Chiefly through the agency of man, great numbers of weeds and other 

 plants have been introduced from other states and from foreign countries 

 and each has begun a vigorous warfare for all the room it can get. 



The sequence of natural families in former Michigan Floras followed 

 Oray's Manual which is essentially that of Auguste Pyrarae De Candolle, 

 Most of the reasons given for that arrangement have long since been 

 considered untenable. In the Flora, I have followed Britton's Manual of 

 the Flora of the NortJieni States and Canada, published in April, 1901. 

 In this work the sequence of families is very nearly the same as that of 

 Engler and Prantl, which is considered the most philosophical yet pre- 

 sented. 



Some of the guiding principles for the system of Engler and Prantl, 

 as they are stated by Britton and Brown's Flora, are as follows : 



The more simple forms are, in general, distinguished from the more 

 complex. (1) by fewer organs or parts; (2) by the less perfect adapta- 

 tion of the organs to the purposes they subserve; (3) by the relative 

 degree of development of the more important organs; (4) by the lesser 

 degree of differentiation of the plant-body or of its organs; (5) by con- 

 siderations of antiquity, as indicated by the geological record; (6) by 

 a consideration of the phenomena of embryogeny. Thus, the Pteridophyta, 

 which do not produce seeds and which appear on the earth in Silurian 

 time, are simpler than the Spermatophyta ; the Gymnospermu' in which 

 the ovules are borne on the face of a scale, and which are known from the 

 Devonian period onward, are simpler than the Angiospermu', whose ovules 

 are borne in a closed cavity, and which are unknown before the Jurassic. 



In the Angiospermje the similar types are those whose floral structure 

 is nearest the structure of the branch or stem from which the flower 

 has been metamorphosed, that is to say, in which the parts of the flower 

 (modified leaves) are more nearly separate or distinct from each other, 

 the leaves of any, stem or branch being normally separated, while those 

 are the most complex whose floral parts are most united. 



The names of genera and species are the same as those used in 

 Britton^ j\fanual and where these differ from those in the sixth edition of 



