CHAP, iv.] from 1838 to 1851. 337 



books could now disseminate the new teaching through 

 wider circles, and with these works may be classed von Mohl's 

 treatise already mentioned on the vegetable cell, since it came 

 much into use in a later and special edition, and was made by 

 many teachers of botany the foundation and guide in their 

 lectures. It was now become the fashion to compose not 

 general text-books of botany, but compendia of anatomy and 

 physiology, and thus morphology and systematic botany were 

 neglected, as anatomy and physiology had been in the period 

 immediately preceding Schleiden's time. Whoever therefore 

 wished to consult a complete manual of general botany was 

 for some time obliged to be content with Schleiden's ' Grund- 

 ziige ' ; and this had a great deal to do with keeping alive 

 his erroneous doctrines on cells and fertilisation among 

 general readers, while the professed botanists had long given 

 in their adherence to more modern and more correct views. 

 It is a misfortune in our science to be singularly poor in good 

 text-books, which might have given a general account from 

 time to time of the existing condition of research ; this is one 

 of the reasons why for some time past even official representa- 

 tives of botanical science often differ so much from one 

 another in their fundamental views on method, and on the 

 question of how much has been actually established and how 

 much still remains doubtful in the main divisions of the 

 subject, that a mutual understanding seems often impossible. 

 That a better state of things in this respect prevails in zoology, 

 physics, and chemistry, is certainly not a little due to the many 

 good compendia and text-books, which endeavour to give some 

 account of the progress of those sciences from year to year. 



However, during the period from 1850 to 1870 Schacht 

 and Unger attempted to make the results of modern phyto- 

 tomic investigation accessible to general readers by means 

 of text-books. Such was the nature of Schacht's 1 work, 



1 Hermann Schacht was born at Ochsenwerder in 1824, and died in 1864 

 in Bonn, where he had been Professor of Botany since 1859. 



Z 



