378 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



In the course of the study of these larger collections much inter- 

 esting information has been obtained regarding the Allioniaceae of 

 the United States. Tins will be published in a later paper. 



During the spring of 1910 the writer in company with Dr. J. N. 

 Rose spent three months botanizing along the west coast of Mexico 

 in the States of Sonora and Sinaloa and the Territory of Tepic. 

 Although the season was not the best for the collection of herbaceous 

 plants, many Allioniaceae were obtained, among them two new 

 species, one of Salpianthus and one of Boerhaavia. An excellent 

 suite of specimens was secured of Pisonia capitata, a plant but 

 poorly represented in herbaria and often confused with P. aculeata. 

 These two species well illustrate the value of field work, for, while 

 in the herbarium it is often difficult to separate them, when growing 

 they are distinguishable at a glance by the color of their flowers and 

 the appearance of their leaves. At Mazatlan the fruits of a species 

 of Okenia were secured in abundance. These, although apparently 

 known to the authors of the genus, had not been collected since the 

 original collection and none were to be found in any herbarium. 

 Guaymas, Sonora, was among the places visited. It is a locality of 

 special interest to the student of the genus Boerhaavia, because from 

 its vicinity were obtained the types of no less than four species, while 

 at least six other species have also been collected there. Unfortu- 

 nately the season was so dry that few of the species were found in a 

 growing state, but the dead plants of the previous season were to be 

 seen everywhere. Some time was spent at the town of Alamos, 

 Sonora, the type locality for two species of the same genus, but 

 strangely enough, although several numbers of Boerhaavia were 

 collected, neither of these two was secured. One of the species was 

 found in several other localities later. Of the Allioniaceae reported 

 from the west coast of the Mexican mainland all were collected except 

 Boerhaavia alamosana and Salpianthus purpurascens. The latter 

 has been found in the vicinity of Culiacan, Sinaloa, but was not seen 

 by the writer. 



The material of some of the Mexican species is very scanty and 

 emphasizes the need of more extensive collecting in that vast terri- 

 tory. Still less satisfactory is that from Guatemala and Costa Eica, 

 while of the Allioniaceae of Nicaragua, Honduras, and Panama 

 practically nothing is known. There is much to be learned of the 

 group through careful exploration and field study, which will doubt- 

 less add many species to our list, especially among the shrubby and 

 arborescent genera. 



The only treatment of the Mexican and Central American Allion- 

 iaceae heretofore published is to be found in Hemsley's Biologia 

 Central i-Americana° issued in 1882. In that work 48 species are 



a Botany, vol. 3, pp. 1-9. 



