Preface vii 



special importance to the student of agriculture, are so inadequately 

 dealt with in our Floras. 



The student should first become well acquainted with the 

 structure and functions of the different organs as dealt with in 

 the first two chapters before proceeding to the use of the keys to 

 the leaves, flowers, and "seeds." The study of these chapters 

 should be supplemented by practical work in the field and 

 laboratory with the aid of a good pocket lens and microscope. 



To facilitate reference, in each of the keys the reader is referred 

 to the page upon which the fuller description is to be found. Also 

 in Chapters vn and viii the Genera are arranged in alphabetical 

 order. Those who desire further information should consult the 

 Bibliography given at the end. 



Objection may possibly be taken to the artificial arrangement 

 of the plants and "seeds" as given in the keys. The writer 

 however believes that while such objection would be most valid 

 in any great Flora or systematic work where only the natural 

 affinities should be considered, in a book of the present kind con- 

 venience should take precedence. Neither is it claimed that the 

 keys are infallible, for the fact of variation constantly reminds us 

 that we are dealing with organic nature — with its infinite possi- 

 bilities as regards adaptations — and not with a mere mechanical 

 structure. 



By the kind permission of Messrs A. Constable and Co., of 

 Westminster, Fig. 21 has been reproduced from The True Grasses 

 by Bduard Hackel. Figs. 161 to 165 have been taken from the 

 New Zealand Journal of Agriculture. With these exceptions all 

 the illustrations have been specially drawn or produced by the 

 author for this work. 



My thanks are due to Professor R. H. Biffen, F.R.S., for much 

 helpful advice relative to the general scheme and publication of 

 the book. 



S. F. ARMSTRONG. 



School of Agriculture, 

 Cambridge. 

 July 1017. 



