v1 PREFACE 
they may find necessary or advantageous for the better 
working of the tables, 
The lst 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 Handbuch 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 (Blackie & 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 Agropyrum, 
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. 
a) Mi OW, 
CAMBRIDGE, April, 1901. 
