90 Immigration of Animals and Plants. 
A white butterfly (Pieris Rapz), the caterpillar of which is feeding on the 
cabbage, doing considerable damage, immigrated from Europe thirty years 
ago. Traveling westward he reached Illinois in about 1877, and spread the 
following years over the whole State. 
Now there is left one insect that was generally believed to be of foreign 
origin, the so-called Hessian fly (Cecidomyia destructor). But Prof. Hagen, 
of Cambridge, Mass., in a paper published in the Third Report of? U. 8. Ento- 
mological Commission, 1883, demonstrated that it is impossible that the fly 
could have been imported by the Hessian troops; that it is very probable that 
the fly was here before the war, and that the fly was not known to exist in 
Germany before 1857. . . 
Much greater is the immigration of foreign plants and is increasing every 
year. When I came to Peoria, in 1852, the following foreigners were perfectly 
naturalized and common around town: The Hedge Mustard (Sisymbrium of- 
ficinale), Black Mustard (Brassica nigra), Shepherd’s Purse (Capsella bursa 
pastoris) ,St. John’s Wort (Hypericum perforatum), Purslane (Portulaca ole- 
racca), Common Mallow (Malva rotundifolia), the Spiny Sida (Sida Spinosa), — 
Velvet Leaf (Abutilon Avicenne), Red Clover (Trifolium pratense), Common 
Mayweed (Maruta cotula), Burdock (Lappa officinalis), Common Mullein ( Ver- 
bascum Tapsus), Horehound (Marrubium vulgare), Goosefoot (Chenopodium 
urbicum), the Jerusalem Oak (Chenopodium Botrys), the Mexican Tea (Cheno- 
podium ambrosioides), Lady’s Thumb (Polygonum persicaria), Black Bind- 
weed (Polygonum convolvulus), Curled Dock (Rumex crispus), Hemp (Canna- 
bis sativa); and of grasses, Timothy (Phleum pratense), two species of Era- 
grostis (E. poaeoides var megastachya and E. pilosa), Chess ( Bromus seca- 
linus), Finger Grass (Panicum sanguinale), and the Foxtail (Setaria glauca). 
Of the following species I have seen at that time only single specimens, they 
are now very common and fully naturalized: The Sow Thistle (Sonchus asper), 
Toad-Flax (Linaria vulgaris), the Common Motherwort (Leonurus cardiaca), 
Hounds’ Tongue (Cynoglossum officinale), Stickseed (Echinospermum Lap- 
pula), Sheep Sorrel (Rumex acetosella), Catnip (Nepeta Cataria. 
Before 1860 were first observed Soapwort (Saponaria officinalis), Parsnip 
(Pastinaca sativa), Ground Ivy (Nepeta Glechoma), Corn Speedwell ( Veronica 
arvensis), the Orchard Grass (Dactylis glomerata), now all common. Then a 
number not common, but occasionally found yet: The Rabbit-foot Clover (Tri- 
folium arvense), the High Mallow (Malva sylvestris), the Cow Herb (Sapon- 
aria vaccaria), the False Flax (Camelina sativa), the Moth Mullein ( Verbascum 
Blattaria), the Thorny Amarant (Amarantus spinosus), Panicum glabrum. 
At that same early time were collected in single specimens, but not seen 
since: Rhaphanus Raphanistrum, Inula Helenium, Nicandra Physaloides and 
Rumex obtusifolius. The Ox-eye Daisy (Leucanthemum vulgaris) I collected 
in a single specimen, 1852, at the fence of the Ballance field, and did not see it 
again until last year, 1885, when it reappeared along the railroad track beyond 
the bridge. 
After 1860, but before 1880, arrived, and became since quite common, the 
Water Cress (Narsturtium officinale), the White Sweet Clover (Melilotus alba), 
the Common Chickweed (Stellaria media), the Oak-leaved Goosefoot ( Blitum 
glaucum), and Amarantus blitoides. This plant I took at first for a prostrate 
variety of Amarantus albus, and so did Prof. Watson, in Botany of King’s Re- 
port, published in 1871, but afterwards made it a new species, first published, 
1877, in Proc. Am, Acad., xii, 273, with the note: “ Frequent in the valleys 
and plains of the interior, from Mexico to North Nevada and Iowa, and becom- 
ing introduced in some of the northern states eastward.” There we have an 
eastward migration of an American species. I suspect that another of our com- 
mon plants, the fetid Marygold (Dysodia chrysanthemoides), perhaps at a re- 
mote time, came from the southwest. All the other species of the genus and 
all the genera of the whole tribe Tagetinz are Mexican, partly extending to 
the states and territories west of the Mississippi. 
Less common, but noticed since about twenty years, are the Cow Herb (Sa- 
