THE COMPASS PLANT. 533 © 
the Flora of the Mississippi Valley extends westward as far as our common timber trees do, [celxxi] 
and down into Texas 
In this connection Dr. Engelmann spoke of the change of the character of the original floras 
through the agency of man. On the Atlantic coast and in the adjacent country the English settlers 
evidently introduced many of their weeds, nearly 300 European species being now more or less 
naturalized, more or less widely spread there. Not half of them have thus far made their way to 
the Mississippi, but every year some new immigrants arrive and make themselves at home here. 
Spaniards and Frenchmen brought with them to the Gulf coasts a few other intruders, and Spaniards 
again brought others into California, some of which, e. g. the wild oats (Avena fatua) and the little 
crane’s bill (Erodium cicutarium) have completely overrun the country, so that for a long time they 
were considered indigenous. 
In the great seaports another mode of introduction of foreign plants has lately attracted a good 
deal of attention; I mean that by means of the ballast of ships coming from distant countries, or 
wool, hides, hay, and other products brought by them. Very few of such plants, however, have 
become naturalized or have spread ; they remain only as temporary or adventitious members of our 
ora. 
A recent means of extending the area of plants is through cattle-droves from the southwest, and 
especially through the extension of railroads. In this way a good many southwestern and western 
plants have found their way into Missouri. Such foreign plants often take hold of extensive grounds 
as “ the fittest to survive,” to the detriment of the native flora. 
It is, therefore, important to observe and note the original flora of a new region at the time of 
its first settlement, and then watch the progress of the gradual change which pasturing and cultiva- 
tion of the soil and the various pursuits of man produce. I have to some extent done this in this 
neighborhood, and can say that I have seen great changes in the local flora during the 45 years in 
which I have been acquainted with it. Some plants have disappeared, others have come in, and 
weeds of all sorts have vastly increased: a fit subject for a future paper. — Journal of Proceedings, 
Nov. 19, 1877. 
Ill. THE COMPASS PLANT.* 
From THE GARDENERS’ CHRONICLE, Fes. 26, 1881, n. s. Vou. XV. 
In the paper of January 15, received —— I notice an account of the Compass Plant (p. 74). When [276] 
common here, years ago (it is now driven out by cultivation in this neighborhood), I have often examined it 
with compass in hand. The leaves at their base are arranged, as may be expected, in the ordinary spiral position, but 
during their development the petiole is twisted so that the blade faces east and west, and its edges point north and 
south. The stem-leaves being sessile show at their base their original position, but their midrib is turned about the 
middle, or in the small upper leaves, towards the tip, so that the upper part of the leaf assumes the meridional direc- 
tion, while the lower part remains fixed in its original position. The large flower-heads, on short and very thick 
peduncles, are almost invariably turned eastward. Sir Joseph Hvoker’s remark about the appearance of a plain coy- 
ered with this Silphium [S. laciniatum] from a railroad train is quite correct, and any change in the direction of the 
road becomes visible at once through the altered appearance of the leaves of the Compass Plant. The equal eae 
tion of the stomata on both faces of the leaf is a matter long known to me, and this species of Silphiwm may be readi 
distinguished from all the others by this character. Only s. compositum comes near to it ; all the others have a a 
greater number of stomata on the under than on the upper side. But why is that so? in connection with this it is 
interesting to notice that other Composite with vertical leaf-blades have a similar anatomical structure. This is espe- 
cially the case with Lactuca Scariola,a plant unknown here before, but extremely abundant now of late years in 
waste places. Its leaves not only assume a vertical position, but also a meridional one, similar to those of the Silphiwm, 
though perhaps less pronounced. 
* See also a note on the Compass Plant by Engelmann in Bot. Upper Missouri, Hayden (Tr. Am. Phil. Soc. 1861, xii. 
196). — Eps. 
