.912] The Ottawa Naturalist 159 



nature. Owing to the very fragile character of the specimens 

 some kind of small box, such as pill boxes or cardboard slide 

 boxes, is almost essential to ensure their safe conveyance home. 

 Material from the same "colony" only, should be placed in 

 one receptacle to avoid the mixing of spores which would other- 

 wise ensue and render identification difficult. This applies most 

 strongly to specimens which to the naked eye appear alike, as 

 when microscopically examined these may be found to be 

 different species. The remaining space in the box should be 

 packed with a little tissue or other soft paper, or failing this, with 

 leaves, to prevent damage to the material by shaking. The 

 conditions most favourable for a plentiful crop of slime-moulds 

 are moisture and warmth. Frequent showers during warm 

 weather furnish ideal conditions. During the hot, dry weather 

 towards the middle of last summer very few specimens were to 

 be found, while in autumn they once more became abundant. 

 The species in the subjoined list recorded from King's Mt. were 

 all collected in October, and so late as October 28, a species not 

 previously met with was collected, somewhat damaged, but 

 still readily recognizable. 



It was at first intended to give a somewhat more extended 

 account of the structure and habits of the members of the group, 

 but on account of their diversity this would necessitate a much 

 longer article than has been thought desirable, and without 

 numerous illustrations would probably not give much help to 

 those unfamiliar with the plants. A series of specimens, how- 

 ever, illustrating all the species here mentioned and some others, 

 has been placed in the Herbarium of the Division of Botanv at 

 the Central Experimental Farm, and will be very gladly shown 

 to anyone sufficiently interested to pay the Division a visit. 

 Such an examination of actual specimens will give a much 

 better conception of these organisms than any amount of written 

 description. 



A word may be added on the economic importance of the 

 group. As regards most of the species this is quite negligable, 

 but a few are parasitic in higher plants and one is the cause of 

 a very serious disease of clutivated crops. This organism is 

 Plasmodiophora brassicae Wor. which attacks a large number 

 of wild and cultivated species of cruciferous plants, its hosts 

 being, perhaps, limited to representatives of this family. Attack- 

 ed plants first show a peculiar malformation of the root, and later 

 the affected part rots, the plant being stunted in its growth 

 or killed. This disease has received in English the names 

 "club-root", "clubbing", " finger-and-toe", and "anbury", and 

 in French that of "maladie digitoire", designations for the 

 most part denoting the abormal form of the root. It is only 



