Vv 
species but in modifying their growth. Many such species as hem- 
lock, canoe birch, beech, hobblebush, round-leaved cornel (Cornus 
circinata L’Her) and others find less congenial conditions than for- 
merly. The hemlock has declined from a tree second in importance 
in the primitive forests to one of slight importance at the present 
time. Such plants as Hydrophyllum virginianum and canadense, cer- 
tain orchids and many others were no doubt always more or less rare 
or local, but at present they are very rare. In colonial times the wild 
strawberry was quite abundant in Massachusetts, and even less than 
a century ago it was fairly plentiful, but at present it is of no economic 
value except in our western territory. Some of the plants observed 
by Dr. Hitchcock nearly a century ago and included in this list have 
not been found since his time, and others have become rare. On the 
other hand, deforestation and the consequent cultivation of much of 
our soil has modified the environment to such an extent that the wil- 
low, birch, goldenrod, aster, violet, bluet, Lespedeza and a host of 
others are found more abundantly than formerly, and as Prof. Ezra 
Brainerd has pointed out, there is a marked tendency for violets to 
hybridize when growing in the open. | 
Many of our introduced plants were brought from Europe in early 
times. Some of them have been growing without much change for 
many years, while others have so adapted themselves to our condi- 
tions that they have become troublesome weeds. In the past twenty-. 
five years many such plants have been introduced through grass seed 
and by means of commercial relations with other countries. Many of 
the plants which Prof. Tuckerman observed as rare in 1875 are now 
common enough, such, for example, as Stellaria graminea L., Digi- 
taria humifusa Pers., Leontodon autumnalis L. and Cerastium vulga- 
tum L., etc. On the other hand, some of our introduced plants have 
not shown any tendency to spread, and in some cases they have ap- 
parently not held their own. Among such plants might be mentioned 
Tussilago Farfara L., Sedum, buckthorn (Rhamnus cathartica L.),. 
various dooryard weeds and plants used for medicinal purposes in 
former times, such as lovage (Levisticum officinale Koch.), wormwood 
(Artemisia absinthium L.), catnip (Nepeta Cataria L.), horseradish 
(Radicula Armoracia L.), henbane (Hyoscyamus niger L), horehound 
(Marrubium vulgare L.), and Canada thistle, which forty years ago- 
was considered a more or less serious pest, but is not now trouble- 
some. These plants were in former times considered essential by 
most well regulated families, but now, along with the lilac, Lombardy 
poplar, live-forever and the old garden rose, they may be found per- 
sisting under unfavorable conditions, serving merely as landmarks of 
once thriving homesteads. 
