56 



this disease : the straining toward a more complex organization of the exuded 

 juices is made evident here l)_v organic formations winch are missing in 

 honey-dew. These organic formations are still more independent in rust 

 dew (Ftil'ujo vagans). iMnally the disease organism appears in the excre- 

 tions and the forms nearly related to them as a peculiar, complete entity. 

 Parasites belong here — the highest among them, such as some kinds of I^)r- 

 anthus, seeming to have separated themselves entirely from the mother 

 liody." 



Unger's views are also shared hy Xees v. Esenbeck and A. Henry' 

 who state in regaril to puff balls that "the fungi clearly stand here 

 at the lowest level . . . ." "They are correctly considered as the ma- 

 terial of disease, as secretions of the higher plants." "The leaf fungus is 

 formed in general by a coagulation of the juices discharged into the inter- 

 cellular passages." 



Theodor Hartig also wrote his work on the red and white rots of the 

 ]-iiie under the influence of this theory. In this he confirmed first of all the 

 co-operation of fungi (Nyctomyces)-. He traced the production of these 

 fungi to a decomposition of the cell walls. 



Of the works which take up general constitutional diseases and scarcely 

 touch upon the fungi, we will name those by Geiger-' and Lindley* 

 which in all essentials are based upon practical experience. On the 

 ether hand, however, Wiegmann's"' statements are evidently based 

 on microscopic studies and the bearings of chemistry, for example, he 

 states that the pus of the blight, as well as that of canker, contains putric and 

 humic acids, but that that of the blight contains more putric acid. To him 

 both diseases appear non-parasitic in nature and he thinks canker (Caries, 

 Necrosis) always arises from "a stoppage and deterioration of the juices, 

 even if these were never present in excess." Among the causes 

 mentioned are injuries to the roots, or injuries from frost and unfavorable 

 soil conditions, as, for example, "H the subsoil is moist, sour, stony or other- 

 wise unfertile, or contains swamp ore." 



Meanwhile, after Corda's" great work on fungi had begun to ap- 

 pear, Meyen's' "Pflanzenpathologie" was published as a standard, which 

 even now warrants consultation. He divides his material into "External 

 Diseases" and "Internal Diseases." Among the former, besides the injuries 

 due to man and to animals, the formation of gnarls and galls, he includes 

 also phanerogamic and cryptogamic parasites, of which the Ustilagineae 

 and the Uredineae as well as other fungi are treated in detail, according to 



1 Das System der IMlze, Section I. Bonn 1S37. 



- Abhandlung iiber die Verwandlung der polycotylen Pflanzenzelle in Pilz und 

 Schwammsebilde und die daraus hervorgehende sogenannte Fiiulniss des Holzes. 

 Berlin 1833. 



3 Die Krankheiten und Feinde der Obstbaume. Miinchen 1825. 



■* The Theory of Horticulture. London 1840. 



5 The Krankheiten und krankhaften Mifsbildung-en der Gewachse von Dr. A. F. 

 Wiegmann sen. Braunschweig 1839. 



« Icones Fungorum hucusque cognitorum. Prague 1837 to 1854. 



" Pflanzenpathologie. Lehre von dem kranken Leben und Bilden der Pflanzen. 

 Published after the death of the author by Dr. Gottfr. Nees v. Ksenbeck, Berlin 1841 



