74 THE AMERICAN BOTANIST. 



Sensitive Oxalies.— The various species oi Oxalis arc 

 noted for closing their leaves jind blossoms at night and 

 often, also, in clondy weather. It is interesting to note in 

 connection with this sensitiveness to light that four or five' 

 species of this genus are also sensitive to touch, the leaves 

 closing downward as in the night position and just oppo- 

 site to the position assumed by the sensitive Cassia under 

 similar conditions. 



More Red Flowers.— I was interested m what was; 

 said in a recent number of The American Botanist about 

 red flowers and after a little thought wrote the names of 

 four flowers not mentioned in your list. These v^ere the 

 Anagallis arvensis (poor-man's weather-grass), Lonicera 

 sempervirens, Acer ruhrum the maple so familiar to us in. 

 the springtime, and the fire pink, spoken of by Ehvyn 

 Waller in the Note and Comment in the August number. 

 This flower I used to find abundantly in and about 

 Bethany, West Virginia. — Mrs. A. E. Dolbear. 



The Changing Flora. — At least two forces are con- 

 stantly at work changing the plant covering of our planet. 

 The flora of anj^ considerable area is as changeful as the 

 population of a great city. The same number of individ- 

 uals may constantly inhabit it but they are not identical 

 WMth those that inhabited it last year nor with those that 

 will inhabit it in years to come. Nature, herself, is con- 

 stantly assisting one species against another in the 

 struggle for territory, by filling up lakes, drying up 

 swamps and leveling the hilltops ; but this, important as 

 it must be in the accumulated years is as nothing com- 

 pared with that destructive animal, man, who clears the 

 forest, dries up the streams and by his agricultural opera- 

 tions drives out the wild plants and gives place to weeds 

 of foreign origin. These weeds, however, are merely cer- 

 tain of the wild species that are able to thrive in spite of 

 man. Many of our worst weeds are from across the sea, 

 but we have natives, also, that cause endless trouble and 

 some have actually gone abroad to compete with the 

 foreign w^eeds in their own territory. 



