72 



" The Culture Methods of Studying Plant Rusts ", by Mr. 

 F. D. Kern : 



The first experiments in the culture of plant rusts were made 

 by DeBary and Oersted in 1865. For a number of years after 

 this many botanists were very skeptical. It was not an easy 

 matter to believe that what had been considered separate and 

 distinct genera of parasitic fungi could really be only different 

 stages of one species. Through the work of a number of 

 mycologists the study of rusts by means of cultures has been 

 advanced with results that are now well known. The methods 

 employed by the bacteriologist are familiar. He makes up arti- 

 ficial culture media of various sorts, and from a sowing of a cer- 

 tain kind of bacterium he obtains a crop of the same sort, if his 

 culture is a successful one. With the rusts the story is quite a 

 different one. They are strictly parasitic and living plants must 

 take the place of culture media. The best success has been 

 attained by carrying on the work under glass. Potted plants 

 with vigorous roots and rather small tops are most desirable. 

 The proof that different forms on unlike hosts are only stages of 

 the same species is obtained by sowing spores taken from one 

 host on another host and raising a crop of spores wholly unlike 

 the ones sown. Take for example the rust of corn {Zea Mays). 

 It has been found by means of cultures that the spores formed 

 on the corn leaves in the fall cannot be made to grow upon corn 

 again. One spring recently it was noticed that some sorrel 

 {Oxalis) plants growing near a pile of rusted corn stalks were 

 badly infected with rusts. From this observation in the field 

 it was thought possible that the corn rusts might be associated 

 with the Oxalis rust. Such proved to be the case. The spores 

 taken from the corn will produce rust on the (9;r«//i" and, vice 

 versa. There is much need for further studies and observations 

 of this sort. The cultures are best made in a greenhouse with 

 plants that are grown in pots. Suggestions as to relationships 

 must, however, be obtained in the field and there is an oppor- 

 tunity here for much valuable work. 



The auditing committee reported that the books of the treas- 

 urer had been examined and were found to be correct. 



Percy Wilson, Secretary 



