27 



BLOSSOM INFECTION IN BARLEY. 



We now turn to the experimental infection with the loose smut of barley^. The smut in 

 its outward appearance and in the form of its spores cannot be distinguished from that of wheat. 



Blossom infection of the barley plant cannot be carried out so easily as that of wheat. In 

 only a few varieties of barley do the blossoms open in such a way that the stamens protrude. 

 In most cases they remain enclosed in the blossoms, that is, inside the glumes, which, how- 

 ever, are wide enough open to make possible a dusting on of the spores. In infecting the 

 separate blossoms of barley the period must be exactly observed in which these are the widest 

 open, because at this time the introduction of the spores can best be carried out. In any case the 

 attack which must be made on the blossoms for this purpose is much greater than in wheat, and 

 it is self-evident that by this means an impediment to infection is caused. For cylinder infection 

 only the splits are to be taken into consideration which are found naturally in the blossoms. 

 Here too artificial infection is, under certain circumstances, less easy than wheat. As above, for 

 the separate infection, only infected blossoms are left standing, all others are removed and 

 the single stalks marked with colored threads. This last was done also in cylinder infections. 



The ripe grain was collected from both series of experiments, kept dry during the winter, 

 sterilized in spring and sown on sterilized vitreous sand, just as was stated for wheat. As might 

 have been supposed, the results of the infection of the separate blossoms were, on an average, not 

 so favorable as those of wheat. Nevertheless, we obtained here, as may be seen at the end of 

 this section from the subjoined comparative survey of our experimental infections, a high per- 

 centage of smutted plants, even up to total infections. (Fig. i, plate i.) 



As shown in the survey, cylinder infection also gives somewhat poorer results than was 

 the case in wheat. At the most they did not exceed 20 per cent. In the separate varieties of 

 barley used for this infection, fluctuations were found, as may be seen from the survey. On 

 the whole, however, the result of blossom infection was approximately as favorable as that 

 with the loose smut of wheat and, favorable conditions being taken for granted, it can be assumed 

 here with certainty that blossom infection is always successful if the smut spores succeed in get- 

 ting into the blossom. 



Infection of young germinating seedlings was carried out in the same four ways as with 

 the loose smut of wheat, with much the same negative result as was obtained with wheat. In all 

 these experiments healthy plants free from smut were formed. In the comparative survey are 

 summarized the series of experiments and their results. Accordingly it holds good for the loose 

 smut of barley, as was said above for that of wheat, that the infection in the blossom is the pre- 

 dominant form of infection of the host plants, if not the only ant. Also the anatomic conditions 



1. The loose smut of barley, concerned here, must not be confused with the covered smut which 

 also occurs in barley, but does not become dusty and remains enclosed in the beard. This smut form, as 

 I have proved by cultivation, differs essentially from loose smut. The spores germinate fructificatively 

 and form conidia, which increase unceasingly in nutrient substrata, in the form of yeast. ROSTRTJP has 

 designated this form, from its external constitution, as Ust. Jensenii. 



