It frequently happens that, because of differences of 
opinion or incomplete information, two or more names are applied 
to the same species. In such cases the oldest name is the one 
properly employed. Because of other references it is sometimes 
desirable to cite in parentheses the synonyms which are or have been 
employed by other authors. In the present paper these appear at the 
end of the species description. 
THE USE OF KEYS: 
Each family with more than one genus, each genus with more 
than one species and the entire system of families herein have been 
provided with keys to assist in the determination of the name and po- 
sition of any given plant. Such keys are devices to assist, and be- 
cause of the innate variation of living organisms are often faulty or 
incompletely satisfactory. Their fullest usefulness is attained only 
with experience. In the present keys we have sought insofar as pos- 
sible to use characters which will permit determination of the plant 
whether in flower or fruit and often, from foliage alone. 
It will be observed that the keys consist of a series of al- 
ternatives, each alternative consisting of a pair of contrasted char- 
acters. Rarely are there three alternatives to choose from. For sat- 
isfactory ~esults it is necessary to study the plant critically and 
completely before consulting the key. After this the first pair or 
contrasted characters is approached. 
YS 
