INTRODUCTION OF FOREIGN WEEDS. 21 
lows in 1875, I find I have appended, as a memorandum to the 
entry : “ The weather has been most remarkably mild, and very 
wet. Wind variable.” 
Now, to take the other side — the arrivals of the spring 
migrants. Here are a few observations, kept at Bromley 
Common for fifteen years, of two or three of the ordinary mi- 
grants, from which will be seen how extremely regular they are 
in their appearance. If it was possible for any one observer to 
catch the first arrival, no doubt the regularity would be found 
more remarkable ; but an observer may see, for instance, a 
nightingale hopping on his lawn, and not see another for a 
week or ten days. Had he not, by mere accident, seen it then, 
his entry for arrival would be, for that year, ten days later ; but, 
in spite of this, the list will show how regular these arrivals 
really are, while the same observer can testify how irregular is 
the autumnal departure. 
I think, therefore, that though any one may jot down in his 
note-book the date of “ the last bird seen,” no practical conclu- 
sions can be drawn from such observations as to any average date 
for the departure of our summer migrants. 
List of Arrivals — 1856-1870. 
Bromley Common, Kent. 
Cuckoo... 
Earliest. 
April 3 
Latest. 
April 25 
Martin ... 
April 19 
April 28 
Nightingale 
April 9 
April 24 
Swallow 
April 9 
April 25 
Whitethroat ... 
April 16 
April 28 
Wryneck 
April 3 
April 18 
THE INTRODUCTION OF FOREIGN WEEDS. 
By GEORGE NICHOLSON, A.L.S., 
Curator of the Royal Gardens , Kew. 
{Concluded from page 6.) 
KjPE^S'RIGERON CANADENSE, the Horse-weed or Butter- 
S firtfa weed of the Northern United States, is quite at home 
in the neighbourhood of Kew, and in many parts of 
England, and is not at all likely to disappear. This 
weed is, at the present time, spread over a considerable portion 
of the earth’s surface. It is said - that it first found its way to 
Europe in the middle of the seventeenth century ; a single seed 
discovered in a stuffed bird was sown, and the descendants 
of this solitary stranger soon distributed themselves throughout 
Europe, and took possession of places to which they had never 
been conveyed by man. Another North American plant — a 
much handsomer one than that which I have just mentioned, and 
