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PREFACE vii 
fungi, it now signifies less than formerly whether the 
Rusts are regarded as related to the Ascus Fungi or the 
Basidium Fungi. As will be seen in Chapter XIII we 
still hold to the theory that their relationship is some- 
what closer to the former than the latter. 
For many years it has been evident to us that the 
apocarpous Flowering Plants must be regarded as primi- 
tive and that from these the syncarpous forms arose. 
Moreover the apopetalous preceded the apetalous 
flowers, the latter being derived from the former by a 
simplification of the flower structure. The flowers of 
willows, oaks, elms, nettles, etc., are quite simple, but 
they are not primitively so: they have been simplified 
from more complex structures, and are to be associated 
with the latter, rather than given place near the beginning 
of the phylum. 
The diagrammatic illustrations used in this book are 
similar to those used on our lecture room blackboards. 
We have felt that in a textbook involving laboratory work 
elaborate drawings were unnecessary and often subject 
to grave abuse. 
It is scarcely necessary to-day to insist that this book 
requires a botanical laboratory; nor is it necessary to 
give “forms”’ to be followed by the student in his labora- 
tory work; for it may be assumed that no one will attempt 
to use this book who has not himself received training in 
a good laboratory. We have purposely suggested many 
more laboratory exercises than can be performed by the 
ordinary student, affording the teacher a large list from 
which he may make his own selection. A few suggestions 
here as to this laboratory work may not be out of place, 
as follows: (1) Have each pupil prepare his own speci- 
mens, as far as possible; only in a few special cases should 
he make use of specimens prepared by some one else. 
