General Introduction 31 



alone for the minuteness, completeness and accuracy of its 

 description of the genera. It is a monument to the greatest 

 of British systematists. 



Mention should be made also of two books which were 

 the earliest efforts that attempted to deal with the pathology 

 of plants. They were Frank's Krankheiten der Pflanzen, 

 published in 1880, and as a second edition in 1884, and 

 Sorauer's Pftanzenkrankheiten, which appeared in 1886. 



The period 1860-1900 witnessed the deaths of many 

 botanists of the first rank, to whose labours in the laboratory 

 the science owes its new revival, and to whose writings the 

 great movements of the new century are deeply indebted. 



Von Mohl passed away in 1872. It is difficult to speak 

 with sufficient admiration of his work, which extended over 

 so many years and did so much to establish the new views. 

 His researches were mainly histological ; he may be said to 

 have utilized to the utmost the development of microscopic 

 appliances in their application to the minute internal struc- 

 ture of the plant. His name will always be associated with 

 the term protoplasm, which though not originally due to 

 him was applied by him to the living substance of the plant. 

 He was one of the pioneers who insisted on its study. 

 Von Mohl's writings show him to us as a model of clearness 

 and especially of fairness in controversy ; they always 

 carefully review the contributions of others while setting 

 out the problems under examination from his own point 

 of view. 



The year 1887 was marked by the death of Boussingault. 

 Though not strictly speaking a botanist, he contributed very 

 largely to the development of the physiological side of the 

 science. His agricultural papers were of the greatest im- 

 portance, especially those dealing with the supply of 

 nitrogen to the green plant. 



De Bary survived Boussingault only a year, passing away 

 prematurely in 1888. His work was very varied, but it 



