RECENT ADVANCE IN THE STUDY OF FUNGI 531 



and for this reason alone mycorhizae and fungal hyphse gene- 

 rally are of enormous importance in plant economy. 



Fungi are overwhelming by mere force of numbers : over 

 50,000 forms have already been recorded and described ; and, 

 as much territory is still unexplored fungologically, the lists of 

 new genera and species still to be added to the world's flora 

 assume alarming proportions. Even in our own well-searched 

 Islands new species are found year by year. The pursuit of 

 this branch of the subject knows, as yet, no pause. All this 

 collecting and describing, this spade-work of the science, must 

 however be done before a true and lasting knowledge can be 

 attained. Close on the heels of the collectors and systematists 

 follow the more critical workers, who examine and compare, 

 and on the data supplied build up a coherent system. 



Thus E. S. Salmon, in recent years, has monographed the 

 Erysiphece on morphological lines. He has found that many of 

 the species recorded, though growing on different hosts, are not 

 really autonomous ; he has given them their true position as 

 synonyms of species already described, and has thus largely 

 reduced the number of species in that family. Another order 

 of work, carrying much the same results, has been undertaken 

 by Von Hohnel, who publishes, now and again, notes on 

 various species, pointing out synonyms and deleting redundant 

 descriptions. 



One of the most notable of recent works on fungi is Klebahn's 

 Hetercecioits Uredineoe, an exhaustive treatise on the rusts that 

 grow at different stages on different hosts. His work has 

 formed a starting point for further effort, and has given a 

 great impetus to students of this group. All advance on this 

 line is by continual inoculation experiments from one host-plant 

 to another. The work is slow and often disappointing, but 

 successful results are constantly being published, and the 

 number of species, in which the life-cycle has been followed 

 throughout, is increasing rapidly. 



Klebahn has also taken up as a study the life-histories 

 of Ascomycetes. They have frequently — if not always — both 

 pycnidial and conidial forms in addition to the perfect fruit, 

 the apothecium or perithecium with the asci and spores. He 

 has added several instances of relationships to those already 

 known ; but here again the work is slow, and results are 

 uncertain. Tracing out these life-histories, and so linking up 



