VI PREFACE 



they may find necessary or advantageous for the better 

 working of the tables. 



The list of the chief authorities referred to, which 

 students who desire to proceed further with the study of 

 grasses should consult, is given at the end. 



I have pleasure in acknowledging my indebtedness to 

 the following works for illustrations which are inserted by 

 permission of the several publishers : — Stebler's Forage 

 Plants (published by Nutt & Co.), Nobbe's Handhuch der 

 Samenkunde (Wiegandt, Hempel and Parey, Berlin), Harz's 

 Landwirthschaftliche Samenkunde (Paul Parey, Berlin), 

 Strasburger and Noll's Text-Book of Botany (Macmillan & 

 Co.), Figuier's Vegetable World (Cassell & Co.), Lubbock's 

 Flowers, Fruits and Seeds (Macmillan & Co.), Kerner's 

 Natural History of Plants (Biackie & Son), and Oliver's 

 First Book of Indian Botany (Macmillan & Co.). 



It is impossible to avoid the question of variation in 

 work of this kind, and students will without doubt come 

 across instances — especially in such genera as Agropyriim, 

 Festuca, Agrostis and Bromus — of small variations which 

 show how impossible it is to fit the facts of living 

 organisms into the rigid frames of classification. It may 

 possibly be urged that this invalidates all attempts at 

 such classifications : the same argument applies to all our 

 systems, though it is perhaps less disastrous to the best 

 Natural Systems which attempt to take in large groups 

 of facts, than to artificial systems selected for special 

 purposes. Perhaps something useful may be learned by 

 showing more clearly where and how grasses vary, and 

 I hope that the application to them of these preliminary 

 tests may elucidate more facts as we proceed. 



H. M. W. 



Cambridge, April, 1901. 



