10 USTILAGO AVENAE AND USTILAGO LEVIS 



In tests on the comparison of smutting" in plants produced from the 

 inner grains of the spikelet with that in plants produced from the outer 

 grains, Arland noted that the inner grains produced from three to four 

 times, and in some cases from ten to twenty times, as many smutted 

 plants as did the outer and larger grains. 



ZADE'S STUDIES, 1912 4 



Zade (1924) published a second paper which is a revised statement 

 based on the investigations published by Arland. It appears that Ar- 

 land, and also Diehl and Roesch, who published their theses later, were 

 students working under Zade. Reference is made by the last two men 

 to an unpublished thesis by Xeumeyer, and, since Zade remarks that the 

 blossom-inoculation work was carried out at his suggestion by Xeu- 

 meyer, it is assumed that his paper (which the writer has not seen) covers 

 in general the same investigations as are discussed in Zade's first paper 

 (1922). 



Since the foregoing account of Arland's studies covers all of the es- 

 sentials given in the second paper by Zade, that paper is not discussed 

 here in detail. It may be well, hoAvever, to mention the conclusions 

 which Zade drew at that time. These were as follows: 



The seat of the resting mycelium may be: (1) the parenchyma of the 

 glumes; (2) the epidermis of the pericarp, where the mycelium is very 

 weak and only superficially or seldom, present; (3) in naked oats. I lie 

 hairs of the caryopsis, where the mycelium is interwoven with them ; 



(4) the remains of the anthers and the stigma, without exception; and 



(5) the remains of the lodicules, only seldom. 



Zade believes that, in the case of naked oats, there is no possibility 

 other than that infection of the seedling results from spores, and also 

 mycelium and gemmae, which are on the epidermis of the caryopsis. 

 This, he says, remains to be investigated. He states that he has sug- 

 gested to Roesch (whose work is considered later) a method of inocu- 

 lating glumes which will prove whether the resting mycelium and the 

 gemmae are or are not actually the true inoculum for seedling invasion. 

 So far, he says, this has only been assumed. 



DIEHL 'S STUDIES, 191M 



Diehl (1925), continuing the work on oat smut and following in gen 

 eral the methods of Zade and Arland, came to the following conclusion : 



Germination of the spores takes place most promptly on the moist, 

 stigma. If the weather is wet and cool, sporidia are produced; if it is 

 warm and dry, the spores germinate directly into germ tubes. How- 

 ever, if the moisture within the flowers is sufficient, the spores may ger- 

 minate even if they do not come in contact with the stigma. Only in 



