376 



thiit aec-iospores were produced on Berhciis froin intVclious from telio- 

 8i)ores of Pucciniw jHjculifonnis lidiii wheat, and thus definitely estab- 

 lislied heteroecism in the T'redineac in 1n(!4. lie also showed that uredi- 

 uiospores followed by teliospores were produced on wheat by sowing aeclo- 

 spores from the barberry. DeBary's radical discovery was rather slow- 

 in. being accepted by many other botanists, yet his evidence was indis- 

 putable and his interpretation prevailed. 



Oersted, working independently and contemporaneously with DeBarry. 

 established similar alteration of spore forms on different hosts between 

 the genera (Jiniinosiwrang'mm on cedars and Rocstelia on the apple family. 



This was epoch-making work in this line and showed the necessity 

 for accurate observations and most careful cultures to show the definite 

 relationships of the different aecial forms. This work was taken up by 

 botanists both in the old and new world and is still being carried on with 

 nuich success. Early workers in Europe, beside DeBary and Oersted, 

 were Fuckel, Magnus, Schroeter, Wolff, Eostrup, Winter, Xielsou, Reich- 

 ardt, Ilartig, Kathay. C(U-nu and Plowright. More recent workers of the 

 (lid world are Fischer, Ivleltahn. Tranzscliel, von Tuheuf, Wagner. Bubak, 

 Juel, Ilennings, Eriksson, Dietel, Liro and others. 



In America Farlow and Tliaxter did pioneer work, follnwcd later, and 

 with greater success, in this line by Arthur, Kellerman, Clinton, Kern 

 and others. The work of Dr. J. C. Arthur stands out prominently above 

 all others. 



The methods used by the different workers are, in the main, very 

 similar, viz: germinable spores of one stage are placed on sterile phmts 

 of the suspected alternate host. Conditions of heat and moisture being 

 kept as favorable as possible throughout. In the methods ust^l by l)r. 

 Arthur, the i)erfectly healthy potted plants are kei)t covered with bell- 

 jars for three days after the spore sowing is mad(\ Each day the bell- 

 jars are removed for five minutes or so to allow llie entrance of a fresh 

 sup])ly of air, after which they are sprinkled within and replaced over 

 the plants, and the plant thus covered is left in a shaded place until about 

 a day after the bell-jar is removed. The inoculated leaves are then kept 

 well moistened and kept out of too strong light and carefully watched 

 for spore developments, ('specially after the first week. If the culture is 

 successful the first simre structure will usually be evident in ;i week or 

 ten days, followed latei- by the second sjiore structure, wIumi that is pres- 



