r.Y F. W. AVAKKFIKLP. 2!) 



The fungi selected for study were Manosporium 

 cladosporioides, Desni., and Alternaria Jirassicie (Berk?), 

 var. Citri, Penz. Cultures of the former were prepared on 

 onion leaves, and were eight days old when the measurements 

 were made. Conidia of the Alternaria were obtained from a 

 fine growth of that species which had appeared on a man- 

 darin which had been under observation in a culture dish. 

 Care was taken that all the conidia measured in the series 

 were taken from the same culture, the same colony or 

 centre of infection, and approximately at the same time. 



Five hundred and forty Macrosporhim conidia were mea- 

 sured, and 321 of Alternaria, making a total of 861 measure- 

 ments. These measurements are tabulated in the table 

 below, which also shows the frequency of occurrence of 

 conidia of certain dimen.sions. It will ba observed that the 

 conidia of MacrosporiMm cladosporioides vary in length from 

 17/u. to ")l/x.. and that the limit of variation observed in 

 Alternaria Brassies', var. Citri, was !)m. to 44fj.- The dis- 

 tribution of frequency in the two cases presents differences 

 which are at once apparent, but they are more strikingly in 

 evidence when the results are plotted. (See graph.) 



SPORE-MEASUREMENTS OF MACROSPORIUM AND 

 ALTERNIA. 



MACROSPORIUM ALTERNARIA 



, , ... -^ llrassicse (Berk?), Sacc, 



ciu<losporiomes, Desm. ^•, • t> 



var. Citri, Penz. 



