282 NINETEENTH REPORT. 



in diameter. As it grows older it darkens to a brown or fuliginous color 

 and attains a diameter of l. 0-5.1 microns. Within the tissues of the 

 well developed spot the mycelium is sparingly branched and does not 

 exhibit the modifications which appear in culture. The types of mycelium 

 found when the fungus is grown on culture media of the various sorts 

 will be described later. 



In comparing the organism studied with those described by Cavara 

 and Malkoff, several ditt'erences may be noted, especially with regard to 

 the size of spores and the lengths of conidiophores. The following is a 

 comparative table: 



Table 1. 

 Measurements of Spores and Conidiophores. Comparison of Published 



Records with Michigan Material. 



a These ligures are the averages of 217 measurements made upon spores grown on 

 seven different media; age of cultures 1 to 3 weeks. 



b Average of 58 measurements made from four of tlie above cultures. 



Since Cavara makes no mention of having cultured the fungus his 

 measurements Avere evidently made from that growing on the host. It 

 will be noted that his spore and conidiophore sizes are smaller than 

 those of both Malkoif and the author, especially in regard to the width 

 of the spores. A specimen issued by Briosi and Cavara^ was available 

 for examination. The few spores which were found when measured, 

 agreed fairly well with the size he gives. The measurement of only a 

 few very old spores cannot be considered as a criterion, but there is no 

 reason to believe that Cavara was mistaken in his measurements. It is 

 possible, however, that he measured the very young spores. The figure 

 which accompanies the herbarium specimens looks very much like that 

 of a young spore. 



The measurements of Malkott' and those of the author agree closely 

 enough, so that at least in this respect they may be considered the same. 

 The author lias measured the spores from material collected in various 

 parts of the United States and finds that they agree in size with tliose 

 found in East Lansing, Mich. 



'Briosi and Cavara — I Funghi parassiti delle piante coltivate od utili. 116. — Mncrosporinm 

 sarcinaeforme Cav., in Difcsa dia parassiti N. 4. Milano 1890. 



