PREFACE II 



a fair general notion of their activities before they 

 enter, later in their medical course, upon the highly 

 specialised study of the disease-producing forms— 

 which are, after all, from the general biological 

 standpoint, a relatively unimportant fraction of the 

 group. The saprophytic and parasitic fungi are next 

 dealt with, and then the more detailed study of 

 the chlorophyll-bearing plants is entered upon, and 

 occupies the rest of the book. Here the evolutionary 

 series is roughly followed, for it seems to the author 

 that the interest and educational advantage of this 

 method of treatment are decisively in its favour. 



The Chlamydomonas-Volvox series is dealt with 

 in much more detail than is usual, because of the 

 unique interest of this series as illustrating the origin 

 of sex and of the soma. Fucus is taken as the best 

 example of primitive tissue differentiation in a relatively 

 large plant, Pellia as a simple land plant. The 

 archegoniate plants are treated very briefly indeed, 

 detailed descriptions of structure and development 

 being deliberately omitted, though an attempt is 

 made to give, in very brief outline, the fundamental 

 facts of the biological significance of vascular plants 

 and of heterospory. 



The rest of the book deals with the Seed Plants, 

 first with their external form and methods of vegetative 

 propagation, then with the architectural elements of 

 which they are composed — a course which has been 

 found very useful in practical teaching because it 

 relieves the later descriptions of the structure of the 

 plant organs from being overloaded with accounts 

 of the tissue elements themselves. The vegetative 

 organs of the plant — root, leaf and stem — follow, 

 and the account of the vegetative structure of the 



