50 THE AMERICAN BOTANIST. 



Rudbeckia 11:89- Scarlet flowers and drouth 13:68. The 

 yellow fringed orchis 11 :45, cream colored jewel weeds 7 :29, 

 66, Color of flowers and locality 9 :76. A yellow trillium 

 12:83. Color variations in a common trillium 11:16. Tem- 

 perature and the color of lilacs 5 :78. Drouth and the color 

 of clover 5:36 viola selkirkii 11:17. Blue hydrangeas 4:15. 

 Locality and the color of flowers, 8 :93. Change of color in 

 flowers, 8 :116, more red flowers 7 :54, color 8 :91. Any single 

 volume may be had for 50 cents or for 40 cents when ordered 

 with a year's subscription. The numbers are not sold singly. 

 Prices of complete sets may be found in the advertising pages 

 or will be sent upon application. Lists of other titles appear in 

 earlier numbers. 



Canada Thistles and the Law. — The Canada thistle, 

 {Cnicus arvensis) which, by the way, is not indiginous to 

 Canada at all but comes to us, like so many of our vile weeds 

 from Europe, is justly considered one of the greatest nuisances 

 with which the farmer has to contend and several states have 

 enacted laws which impose severe penalties upon any person 

 allowing these plants to go to seed upon his premises. No 

 little confusion exists, however, as to the best way of eradicat- 

 ing these weeds when they once gain a foot-hold. Farmers, 

 in general seem to think that an application of a heavy dose 

 of salt is the only effective method while a few claim that salt 

 acts only as a fertilizer to them- It is strange that notwith- 

 standing their familiarity with growing things very few 

 farmers seem to realize that any green plant may be killed 

 by simply cutting off its leaves and allowing no more to form. 

 Canada thistles are as easily killed by this method as any 

 other plant, though owing to the amount of food stored in 

 their underground parts, it may require several cuttings of 

 the leaves to finish the job. It is often stated that the Canada 

 thistle does not mature its seeds in the southern parts of its 

 range, but this is a mistake founded upon a misunderstand- 



