— 22 





gates, as all this will be found in the report of the Ontario Entomological Society 

 for 1913. 



The only thing I wish to mention is the cordial reception we received from 

 the President and several of the professors of the Ontario Agricultural College, 

 the Officers of the Ontario Entomological Society, and the Grimsby orchard 

 owners, for which we are very thankful. 



THE WHITE CYSTOPUS. 

 J. C. Chapais, St. Denis-en-bas, P. O. 



Everybody who owns a garden knows the noxious weed commonly called 

 "Shepherd's Purse," in French Boiirse-a-pastciir, but, in case some one should 

 not know it under this appellation, I will give here a brief description of it, as I 

 am going to mention it in the short note I wish to write concerning the white 

 Cystopus. 



Description. — Names : Capsella Bursa Pastoris. — Shepherd's Purse, Cap- 

 selle, Boiirse-a-pasfeur. Introduced from Europe. Annual and winter annual. 

 Few plants are so variable in size and appearance. It may be bright green and 

 nearly smooth, or gray from very short appressed hairs. A seed-bearing plant 

 may be a dwarf, little more than an inch or two high, or a vigorous branching 

 plant, three feet high, with many pods. There may be at the base a vigorous ro- 

 sette of leaves, or none at all. The leaves may be deeply cut, pinnatifid, or with- 

 out any teeth or division. The stem-leaves are for the most part arrow-shaped, 

 with two sharp ear -liked projections, one on each side of the stem. The flowers 

 are small and white. The only part of the plant which seems to be constant is 

 the seed-pod, which is flat, triangular in shape, one-fourth of an inch long, wedge 

 shaped at the base, notched at the top, with the outer angles rounded. Each pod 

 contains about twenty seeds. (Farm Weeds of Canada). 



I have just stated that it is on account of the white Cystopus that I have men- 

 tioned Shepherd's Purse. This plant of the Cruciferous family, is the favorite 

 foster-mother of that fungus commonly nam.ed cabbage mildew and which is 

 nothing else than the white C3^stopus (Cystopus candidus). Here is what we 

 find in ''The Century Cyclopedia" about the Cystopus : "It is a genus of parasitic 

 fungi, belonging to the family Peronosporeae, and characterized by conidia 

 produced in chains on very short conidiophores, forming compact sori upon the 

 supporting leaf." Cystopus candidus is injurious to the cabbage, radish and 

 other cruciferous plants. I have very often found it on Shepherd's Purse, and 

 four or five times during my life time, I have seen its attacks on cabbages and 

 turnips. In fact, this fungus will feed o nail crucifer plants. As it is seen in 

 greater quantity than usual this year, I thought that it would be valuable to call the 

 attention of gardeners to it, especially as it is seldom mentioned in our horticul- 

 tural literature. While giving here its description, I have before me a plant of 

 Shepherd's Purse which is covered with it, and at the same time, I am guided by 

 an article of Mr. E. NofTray, printed in "Le Journal d'Agriculture Pratique" of 

 Paris, France. 



The White Cystopus shows itself as white pustules on the leaf petioles, some 

 pustules of which are seer also on the limbs of the same leaves. These pustules 

 are as many as 18 to 25 on an inch. The conidia of these pustules emit zoospores 

 which produce by germination mycelial filaments having a deforming property, 



