Hill : Notes on Plants of the Chicago District 309 



the river valley. The cliff also furnishes me the only station 

 for a pretty liverwort, Grinuildia harbifrons Bisch., its forking 

 thallus forming little patches on the thin soil of crevices. Poly- 

 gonum cxscrtion Small may be mentioned In this connection, 

 like Pentstemon pubcscois frequenting the rocky soil of the valley 

 floor both here and at Lockport. 



In the field of introduced plants novelties may continually be 

 expected. It is well to note their arriv^al as nearl}- as possible, for 

 the migration of plants becomes important in giving some idea of 

 their habits and rate of spreading. As an example the Yellow 

 Cress {Nasturtium sylvestrc) may be cited. In 1890 it w^as foinid 

 near Western Springs, w^est of Chicago. It had not been reported 

 from our region before and seemed quite local, growing along the 

 Avet banks of Salt Creek and by roadsides and in neighboring 

 meadows. Now it is exceedingly abundant along the Desplaines 

 from Riverside to Lamont or beyond. Salt Creek enters the Des- 

 plaines near Riverside, and another stream, Flag Creek, heads near 

 Western Springs, but a short distance from Salt Creek, and enters 

 the Desplaines above Lamont. Either route makes an easy path 

 for the spreading of such a plant, but its habits show^ that it is also 

 provided with other means of migrating. It is a hardy plant and 

 adapts itself to quite a range of conditions : it will grow w^ith its 

 stems half buried in mud and water, and seems equally at home by 

 the roadside where the wagon wheels ma}' bruise it On railway 

 embankments it spreads beside the rails and even roots in the ballast. 

 Under these dryer conditions it is more branching and bushy, or it 

 may be procumbent, leaning on the ground for support. The rail- 

 ways are in fact responsible for most of our introduced plants as 

 well as their dispersion when once established. Some of these 

 plants are weeds which could well be spared, others are harmless 



or may be desirable acquisitions. 



Coming from the east may be mentioned Bronius tectorum L., 

 small and softly hairy, which appears along the railroads east of 

 the city in Indiana. It was first detected in 1897. At the same 

 time Ccutaurea Jacea L. was obtained. Reseda alba L. was col- 



r 



lected last year in the streets of Morgan Park south of the city. 

 Artemisia annua L. w^as obtained the first time last season from 



' ' I 



roadsides at Lamont. 



