APPENDIX. 
During the progress of our investigations much information has been received from 
numerous sources which could not be included in publication at the logical places. Some 
of this was taken up in the appendix to the first volume (Cactaceae 1: 216-225) and some 
in the appendix to the second (Cactaceae 2: 223-226); what remains is included in this 
appendix to the whole work. 
Dr. David Griffiths, who studied the species of Opuntia, especially with relation to 
their economic possibilities, and grew many of them at experimental stations of the United 
States Department of Agriculture at Brownsville, Texas, and at Chico, California, has 
published and described many species as new. We have included these in our studies of 
the genus and have grouped them with the species known to us as accurately as has been 
possible from his published descriptions and illustrations and after examination of as 
many of his type specimens as we have been permitted to see; however, conditions were 
such that we have not been able to study a number of them. They have not been arranged 
for ready reference by students. 
The preface to Volume I gives a list of volunteers who have made valuable con- 
tributions of specimens and data to this investigation. Many of these have continued to 
aid us. 
Dr. Britton, in continuing his West Indian studies, investigated the cacti of Grenada 
and of Trinidad in 1920 and 1921 and published an account of the Trinidad species. 
Dr. John K. Small has continued his investigation of the southeastern United States 
and of Florida in particular, in cooperation with Mr. Charles Deering, and has greatly 
increased our knowledge of the cacti existing there, including the discovery of many 
undescribed species of Opuntia. 
Dr. Francis W. Pennell, Curator of Botany at the Academy of Natural Sciences of 
Philadelphia, and Mr. E. P. Killip, of the United States National Museum, made extensive 
botanical collections in Colombia in 1922, including some specimens of cacti, which we 
have studied. 
Dr. Henry H. Rusby led the Mulford Biological Exploring Expedition to Bolivia in 
1921-1922 and with the assistance of Dr. O. E. White obtained for us specimens of several 
little-known cacti. 
Dr. Philip A. Munz has sent us cacti from the deserts of southern California. 
Mr. C. Z. Nelson obtained cacti from southern Mexico, including a beautiful new 
species of Selenicereus. 
Mr. Francis J. Dyer, while connected with the Consular Service in Honduras and 
at Nogales, Mexico, sent us many specimens from those stations. 
Professor Harvey M. Hall, while making extensive explorations in the western United 
States in connection with his own work, has forwarded interesting cactus plants. 
Dr. and Mrs. Charles D. Walcott have sent specimens from Alberta, Canada, some of 
them coming from near the most northern range of the family. 
Dr. W. L. Abbott and Mr. E. C. Leonard made extensive collections in Haiti in 1920 
and obtained a number of rare and little-known plants, including one which had been 
collected by Charles Plumier about 1698 and which proved to be a new genus; this was 
named by us for Dr. Abbott. More recently Dr. Abbott has sent us specimens from 
Santo Domingo. 
Dr. George F. Gaumer, the veteran collector in Yucatan, has sent very important 
collections from his region, including a number of new species. 
Mr. Ivan M. Johnston, who accompanied the scientific expedition sent out by the 
California Academy of Sciences in 1921 to explore the islands of the Gulf of California, 
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