PREFACE. V 



secure a more logical presentation of the subject, 

 there are but two considerable innovations, consist- 

 ing (I.) in the recognition (in Chapter VI.) of seven 

 quite well marked kinds of tissue. In this, however, 

 while not adopting De Bary's classification, I have 

 followed his method of treating the subject, as given 

 in his recent work on the comparative anatomy of 

 plants (" Vergleichende Anatomic der Vegetations- 

 organe der Phanerogamen und Fame.") (II.) The 

 second considerable innovation occurs in Part II. ; it 

 consists in raising the Protophyta, ZygosporefiB, Oos- 

 poreae and Carposporese to the dignity of Primary 

 Divisions of the vegetable kingdom, co-ordinate with 

 the Bryophyta, Pteridophyta and Phanerogamia. 

 The usefulness of both of these departures from the 

 common practice has been subjected to the test of 

 the laboratory, and the lecture and class-room, with 

 the most satisfactory results ; and I am led to hope 

 that in the hands of others they may also serve to 

 give a clearer and more accurate notion of the struc- 

 ture of plants. Should they do this they will need no 

 further apology or defense. 



Of the illustrations, many are entirely new ; many 

 others have been re-drawn, from various sources, 

 with slight modifications, expressly for this work, 

 and all from other sources are specially acknowl- 

 edged in their places. 



I desire here to acknowledge my indebtedness to 

 Dr. Asa Gray, whom it is an honor to own as my 

 sometime teacher, for kindly aid and counsel in the 

 preparation of the lectures upon which this work is 

 based ; and in the same way I am indebted to Dr. 

 G. L. Goodale, Dr. W. G. Farlow and Professor A. 

 N. Prentiss. For aid in the immediate preparation 

 of the material for the press, acknowledgment is due 

 many of my personal friends : Mr. J. C. Arthur fur- 

 nished the original drawings of the water-pores of 



