P R E F A C E .
T h e papers on which this work is founded were originally communicated
to the Royal Microscopical Society, at the request
o f one o f my friends on the Council ; and it is, therefore, with
peculiar pleasure I dedicate it to them, since without the instrument
which they have done so much to bring to perfection, no
satisfactory investigation o f the subject would be possible.
A s I have been only able to prosecute it as a relaxation
from active professional work, I am aware it must exhibit many
deficiencies and shortcomings ; y e t the dissections and observations
required, have proved to me lessons o f the highest value in
imparting a knowledge o f these interesting plants, which I trust
may to some extent be shared in b y all who make use o f this
record o f them.
T h e drawings o f the plants are all o f the natural size, and
taken from specimens in a moist or expanded state ; the dissections
have as far as possible been copied b y means o f the camera
lucida and Messrs. B e ck’s large instrument with 3 - inch and
f-in ch objectives, and represent the structural peculiarities which
are characteristic o f the different species.
T o Professor Lindberg, o f Helsingfors, I am deeply indebted
for rare specimens and critical observations, and to him and the
various correspondents whose names are recorded under each
species, I b eg to offer my warmest thanks.
C l a p h a m R i s e , L o n d o n ,