38 THE AMERICAN BOTANIST 



the starch is turned to sugar, it increases the osmotic pressure 

 in the cell and in this manner is believed to stimulate the cells 

 into new growth. It is probable that different plants require 

 different lengths of exposure to the cold in order to resume 

 growth. Not only may the effects of chilling be noticed in 

 the mature plant, but it appears in seeds as well. The prac- 

 tice of planting various seeds in autumn may, after all, be for 

 the purpose of exposing them to the cold instead of breaking 

 the siiells as commonly assumed. 



Offensive Luxuriance. — In the English Garden Miss 

 Gertrude Jekyll complains of a number of beautiful plants 

 which, admitted to cultivated ground, thrive so well that they 

 encroach upon better specimens until their room is better than 

 their presence. Since they thrive so well in a variety of soils, 

 they are naturally hard to eradicate. Among such noxious 

 species she lists the common horsetail {Equisetum arvense), 

 the great yellow loosestrife {Lysimachia vulgaris), the com- 

 mon tansy (Tanacetmn vulgare), the field scabious {Knautia 

 arz'ensis), the wood sorrel (Oxalis violacea), the field bellwort 

 {Caiiipaiiiila rapimculoidcs) the goutweed {Aegopodiuin poda- 

 graria), and the enchanter's nightshade (Circaea liititiana). 

 To this list the editor of the Gardener's Chronicle adds the obe- 

 dient plant {Physostegia Virginica), and the purple loosestrife 

 {Lythrum roseum). It is likely that the plants mentioned 

 would n()t prove equally weedy in all gardens, however. The 

 soil often has a considerable influence on the luxuriance of a 

 given species. The writer of this paragraph has found the 

 tawny day lily {Henicrocallis fulva) too pushing for respect- 

 able garden company but considers the day flower {Comniel- 

 yna communis) a far greater pest. Costmarv {Chrysanthe- 

 mum halsamitae) perhaps better known as sweet Mary or 

 rosemary, is another quickly spreading plant, but the worst of 



