160 The Ottawa Naturalist. [Feb. 



too well known in most parts of the world where cruciferous 

 crops are grown, but in this country its occurrence is only known 

 with certainty in the Maritime Provinces, in some districts of 

 which it is very destructive. At the same time from verbal 

 descriptions occasionally given to members of the staff of the 

 Ontario Agricultural College it would seem that the disease is 

 present in Ontario, although its occurrence cannot be looked 

 upon as established until reports are confirmed by specimens. 

 It would be rather strange if it were unknown here, since in the 

 adjacent State of New York it is a very serious pest, especially 

 in the market gardening districts around the large cities. 



Another organism about which enquiries are sometimes 

 made in the belief that it is parasitic, is Spumaria alba. The 

 large fruiting bodies (aethalia) of this species, often 2 inches 

 or more in length, are frequentlv found attached to the leaves 

 and stems of various living plants, and are sometimes found in 

 strawberry plantations. While at the Agricultural College at 

 Guelph the writer received specimens from a strawberry grower 

 who stated that they were present in great quantity on his straw- 

 berry beds and killing the plants. No doubt he was wrong in 

 thinking the Spumaria parasitic, but the aethalia are easily 

 broken up into a powdery mass of calcareous dust and black 

 spores, and hence objectionable amongst the ripening fruit. 

 In France this source of trouble is sometimes so prevalent that 

 spraying with a solution of potassium sulphide is recommended 

 for it. With the exception of these two, however, none of the 

 species known to occur in this country are of any commercial 

 importance. 



In the preparation of the list that follows thanks are due 

 to Prof. Macoun, of Ottawa, and to Prof. Macbride, of Iowa 

 University ; to the former for permission to work over a collec- 

 tion of material in the Herbarium of the Geological Survey, and 

 to the latter for assistance in the identification of difficult or 

 doubtful specimens. The additional localities obtained from 

 a study of Prof. Macoun's material are indicated by an (M). 



The nomenclature adopted is for the most part that of 

 Macbride's monograph, but in a few instances that of Torrend 

 (Les Myxomycetes, 1908) has been preferred. Where the nature 

 of the substratum is not indicated the specimens were gathered 

 on decaying wood. 



List of Species. 



Ceratiomyxa mucida (Pers.) Schroet. Ceratiu u hydnoiJcs 

 A. & S. Although an especially careful lookout was kept for 

 this species during the past season the only specimens collected 

 were some immature and doubtful ones from the Boom Rd., 



