104 HISTORY OF BOTANY 



faction and decay/' This important generalisation was 

 confirmed and extended by Boussingault ten years later, 

 when he showed that plants were unable to make any use 

 of the free nitrogen of the air, but derived all their supplies 

 of that element from nitrates present in the soil, and 

 that plants could be cultivated quite satisfactorily in an 

 artificial soil containing nitrates but from which humus 

 had been entirely excluded. To complete the story, it 

 was shown, about the same time, by Wiegmann and 

 Polstorff that the minerals present in plant ash were 

 essential to the welfare of the plant and were all derived 

 from the soil and from the soil only. 



CRYPTOGAMIC BOTANY IN THE BEGINNING OF THE 

 NINETEENTH CENTURY 



When we were discussing the evolution of the idea of 

 a natural classification of plants you must have noticed 

 how the lower forms of vegetable life were practically 

 ignored, or bundled together, often along with some 

 Phanerogams whose flowers could not be seen or at least 

 could not be recognised as such, into a general rag-bag 

 called Cryptogamia, Cellulares, Acotyledons, and so on. 

 The attention of taxonomists was concentrated on 

 flowering plants and, save for a few isolated observations 

 made during the closing years of the eighteenth and early 

 years of the nineteenth centuries, very little was known 

 of either the structure or the life histories of the Thallo- 

 phyta, Bryophyta, and Vascular Cryptogams. As 

 recently as 1881 the course of instruction in botany in at 

 least one British University consisted of fifty lectures, 

 forty-five of which were devoted to the morphology, 

 physiology (very little of it !), and taxonomy of flowering 

 plants, while the remaining five dealt with the life history 

 of a fern and of a moss and the merest sketch of the 

 differences in nutrition between an Alga and a Fungus. 

 In the first half of the eighteenth century, it is true, 



