1889.] DEPARTMENT OF BOTANY. 4.5. 



HORSE-NETTLE. 



In the last biennial report Dr. Halsted reported the appearance of Horse- 

 Nettle {Solatium Carolinense, L.) on the College farm. This species has 

 certainly come to stay. The past summer it was found in several places on 

 the farm. In Missouri am] Southern Illinois it is a very troublesome j)est in 

 grain fields. The leaves and stem are prickly. The flowers resemble those 

 of a potato; pale bine or whitish in color, while the "seeds" (berries) are 

 yellow. The plant is a perennial, that is, living from year to 3'ear, and 

 therefore somewhat difficult to destroy. The only effective measure of deal- 

 ing with this pest i< to stamp out its first appearance. This may be done by 

 digging it up roots and all, and allowing none of the leaves to grow, as 

 the-e ;irc the organs in which the food of the plant is made. 



SPIN r- NIGHTSHADE. 



Another very troublesome pest, and closely related to the Hor<e-Nettle, is 

 the Spiny-Nightshade (Solatium rostratum Dunal) or thistle as it is called in 

 some places. This weed occurs in parts of Iowa. It is to be hoped that 

 this pest will not get a strong foothold in our loose, fertile prairie soil. 

 The Spiny-Nightshade is a native of the Rocky Mountains, and the plains 

 from Nebraska to Texas. It has spread eastward and southward to a consider- 

 able degree. Prof. Henry has well said, it is following up the "Potato Bug." 

 Anyone who has traveled in Texas or parts of Kansas and Missouri knows 

 how troublesome it is to the farmer. In these States it is well established; 

 occurring in streets, door-yards, and fields. In pastures, cattle avoid it,, 

 thus leaving it to go to seed. Texas parties inform me that this plant 

 scatters its seeds like our tumble weeds (Amarantus, Cycloloma, etc.). 

 How long will it be before it becomes a serious pest in the grain and 

 corn fields of the Mississippi valley? It has already been reported from 

 Wisconsin. New York, and Massachusetts. The Wisconsin plants which I 

 collected were only strays, accidentally introduced by seed. 



PRICKLY LETTUCE VXD FIELD 'SOW-THISTLE. 



From time to time I have made observations on several other introduced 

 plants. I was therefore much interested in a little patch of Prickly Lettuce 

 [Lactuea mcariola, L.) occurring on the College grounds. Dr. Halsted! 

 informs me that he first observed it several years ago near some rubbish on 

 the College farm. I also noticed some in the streets of Ames and Des 

 Moines. The spreading of this weed is rather interesting. In Dr. Gray's 

 Synoptical Flora of North America it is recorded as "spreading near towns 

 and habitations in the Atlantic States." It seems that Mr. Eggert collected 

 it as early as 1877 near St. Louis. Mr. David F. Day found it at Mukwauago, 

 forty miles west of Milwaukee, in 1880 (Bot. Gazette, page 159. See also 

 page 139 for other localities). In the fall of 1883 it was quite common at 

 Madison, Wisconsin, and in 1885 it was plentiful in a good many of the 

 vacant lots in North Chicago. In the summer of 1887, I found it near 

 LaCrosse, Wisconsin, in Vernon county, growing on a manure heap only a 

 few yards from a nursery. There can be little question that it was intro- 

 duced in some way by the nursery man, as much of his stock was purchased 



