300 
Canada thistles, 4008 individuals for 1885 and 3801 for 1886. 
Twenty-two species of 1885 numbering 438 individuals did 
not appear in the plat of this year, while fourteen species. 
with 286 individuals occurred this year and not last. The 
majority of the species peculiar to last year are to be classed. 
among the weeds most commonly met with in borders of 
cultivated fields and in pastures and meadows, while those 
occurring only this year are more characteristic of continu- 
- ously ploughed fields. 
The present year’s observations very well represent the 
condition of clean cultivation of unmanured land, which 
has been ploughed long enough to eradicate most weeds, 
adventitious from its condition as a meadow or pasture, 
and not long enough to become infested with those from 
old cultivated fields. This is practically the minimum 
number of weeds for ordinary cultivation, and amounts to. 
81900 individuals per acre for the growing season. 
IMPORTANT ARTICLES ON PEAR BLIGHT. 
The following list of papers, selected from several hun- 
dred titles forming part of an index to the subject, in course 
of preparation by the writer, is intended to indicate the pre- 
vailing public opinion upon the subject of pear blight from 
the earliest-record yet found to the present time. As the 
index from which it is taken is yet far from complete, it is. 
likely there are other papers that might have been advan- 
tageously added, although the object in presenting it at this 
time is well attained as it stands. 
Brief abstracts of the papers are appended, giving much 
valuable information, but also exhibiting some errors of 
opinion and observation, which the reader will doubtless. 
easily detect. It should be said in justice to the authors. 
quoted, that the selections do not in every case represent 
mature opinions, but rather those standing for the fore- 
~ most thought of the time, or made prominent by the position 
of the writer, or the time or the place of utterance, which 
subseqent information may have materially changed. 
The early accounts are especially important in studying. 
the history of the origin and spread of the disease, and any 
information regarding items or papers printed in the last 
century will be very welcome. 
