a Contributions from the Gray Herbarium 
tion of species from other unrelated genera— Taraxacum and Trago- 
pogon, among others — in their reaction. The chemical reactions 
of plant protoplasm are undoubtedly of value in the discrimination 
of species of lichens, as Prof. Cockerell observes, but their use as a 
touchstone of critical generic values in the highest family of flower- 
ing plants is not likely to commend itself to taxonomists. 
Il. Marertat EXAMINED 
The present revision owes its inception and whatever it may pos- 
sess of completeness to the opportunities afforded by two years 
spent in study in Europe as a Sheldon Travelling Fellow of Harvard 
University, for which my most grateful thanks are due to the au- 
thorities having the administration of the Frederick Sheldon Fund. 
It is a pleasure to acknowledge the uniform courtesy shown and 
kindly assistance rendered by Dr. Otto Stapf and Mr. J. Hutchin- 
son of the Kew Herbarium, Dr. A.B. Rendle of the British Museum, 
Dr. C. E. Moss of the Cambridge University Herbarium, Dr. H. 
Lecomte and Dr. F. Gagnepain of the Paris Museum of Natural 
History, Profs. Engler, Diels, and Volkens of the Royal Herbarium 
at Dahlem, Dr. C. de Candolle of Geneva, Prof. J. Briquet of the 
Delessert Herbarium, and M. G. Beauverd of the Barbey-Boissier 
Herbarium — to many of whom I am further indebted for the gift 
of fragments and photographs of authentic material for the Gray 
Herbarium. Through the kindness of Dr. J. M. Greenman and 
Mr. W. R. Maxon I have also been enabled to examine the material 
in the herbaria of the Missouri Botanical Garden and the United 
States National Herbarium, including many important types. To 
Mr. T. S. Brandegee I am under obligations for the loan of the 
type of Viguiera similis, to Dr. N. L. Britton for the loan of the 
type of V. lanceolata, and to Dr. C. A. Lindman for the transmis- 
sion of fragments or tracings from the types of three species in the 
Riksmuseum at Stockholm. To Mr. F. Schuyler Mathews my 
thanks are due for his care in the preparation of the plates, and to 
Miss Mary A. Day for bibliographical assistance. Especial thanks 
are due Dr. B. L. Robinson, under whose guidance this revision has 
been completed at the Gray Herbarium, for his aid and advice in 
various critical questions, where his extensive knowledge of the 
Compositae has been of great service to me, and to Dr. E.-C. 
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