

PREFACE. VII 



for study, our knowledge of the various forms will still be far from, 

 complete. Their number may be reduced or increased and their 

 relative status altered. Nevertheless, the present paper will remain 

 the first attempt at a thorough study of the group. In recent years 

 new species have been discovered in South America, and the areal 

 limits of the genus have thus been extended far beyond the Isthmus 

 to Bolivia and eastern Brazil. It is almost certain that other species, 

 hitherto hidden in the unexplored forests of South America, will 

 come to fill the gaps in the distribution of the genus. 



Of the two papers comprised in part 8 the first, by J. N. Rose 

 and Paul C. Standley, deals with the Mexican species of Talinum, 

 a genus of portulacaceous plants which has been much neglected in 

 the past, only a few species having been known from Mexico. Studies 

 of living plants in Washington and of accumulated herbarium material 

 however, have enabled the writers* to revise all the proposed Mexican 

 species of the genus and make numerous additions. Of the 18 

 species here recognized, 10 are new to science. The second paper, 

 by J. N. Rose, records two additional species of the recently described 

 umbelliferous genus Harperella. 



Part 9 is a paper by Dr. J. N. Rose in continuation of his Studies 

 of Mexican and Central American Plants. It contains a brief 

 account of his seventh journey to Mexico. Most of the plants 

 discussed are new or recently described species which Doctor Rose 

 discovered in the field or while studying various groups of Mexi- 

 can plants. Some 24 new species of Crassulaceao are here de- 

 scribed. This is a remarkable addition to our knowledge of this 

 group, for the family had been extensively studied during several 

 years prior to 1905, when the North American species were mono- 

 graphed. Some of the present new species are of horticultural 

 interest. Echeveria crenulata, E. holwayi, and E. gloriosa are some- 

 what similar to the well-known E. metallica of our greenhouses. 

 To Urbinia, a recent segregate from Echeveria, two more species 

 are added. One of these, Urbinia purpusii, is a curious plant sug- 

 gesting in habit and foliage the south African genus Haworthia. 

 The plant is worthy of a place in every good succulent collection. 

 In cultivation it has shown no tendency to produce suckers and 

 perhaps its propagation can be accomplished only by seed. 



Part 10 is composed of six short papers. The first, entitled The 

 Gyrophoraceae of California, by Dr. Albert W. C. T. Herre, is a 

 synoptic treatment of the California members of the group of lichens 

 formerly associated under the name Umbilicaria, but now regarded 

 as of two genera, Gyrophora and Umbilicaria, the latter represented 

 in California by only a single species. The second paper, The plant 

 life of Ellis, Great, Little, and Long Lakes in North Carolina, by 

 William II. Brown of the Bureau of Fisheries, was prepared inci- 



