NATURAL ANI AKTIFK IAL INFK(.TIuN. 



odour, '//. Acc. <//v/////// in Amei i< -;t. The wind we must also 

 regard as the distributor of mvdospores and of the sporidia of 

 germinating teleutospores. The rredineae have typical .-pojv- 

 for distribution by wind with tin- exception of the so-called 

 spermogonia. These structures are produced by most rredineae. 

 generally on the upper surface of tin- leaf and before the aeeidia: 

 they are brightly coloured, and give out spermatia in a sticky 

 gelatinous slime, frequently with a distinct odour. Tim- tln-\ 

 seem to be admirably adapted to transport by insects, and are 

 in faet visited by them. Their distribution, however, lias little 

 importance, since they are, as far as known, incapable of 

 germination. They are regarded by many as degenerate forms, 

 either of male sexual organs, or of pycnidia. Some of the 

 spermatia have been made to germinate in artificial culture, 

 but of their incapacity to germinate in natural surrounding 

 there can be no doubt. I am not aware of any one who 

 has succeeded in bringing about infection witli these spermatia. 

 but I have tried it often with no result. 



It is much more ditlicult to ascertain how fungi, whieh 

 hibernate on the earth, find their way in spring to their 

 re.-peetive host-plants, in some cases even to the crown of v<-i\ 

 large trees. Amongst such forms one frequently finds an 

 arrangement by which the spores are forcibly ejaculated. Thu> 

 JUn/H^iii'i acerinum, which reaches maturity only in spring after 

 hibernating on dead sycamore leaves, and X-A /-///// in Intnln,. 

 which does so on fallen fruits of birch, both have their spores 

 forcibly ejaculated and carried oil by wind. Klebahn state- 

 that the ejaculation takes place in dry weather, and that the 

 Spores of ];lii/tixiiin are prevented fmni diving up by a gela- 

 tinou.s eov.-nn;.:. In a similar manner the hibernal in- spores ol 

 Kiv-ipheae on fallen leaves must be carried up again by wind: 

 30 al.-o those of r,>li/*f iijnin, which ripen on the mound and then 

 infect young leaves of plum and cherry trees. 



Infection by means of the mycelium generally occur.- where 

 the mycelium lives in the earth. Thus, the hyphae of '/'/<////./ ^ 

 rinlii-iiH-riln -row rapidly from one root to another, can-in 

 centrifugal spreading of the fun-ii-. 80 that loiv.-ts attacked by 

 it ha\e the trees killed oil' in patches. Mycelial infection is still 



lliol-e effective ill f 1 1 II - i like AgO/nCMA linl/'t/X which a-sllliie t lie 



form of rhizomorphs. Infection by mean- of the mycelium 



