FORMATION AND SUCCESSION HERBARIA I97 



244. Details of collecting:. Formational collections, unlike the ordinary 

 sets of exsiccati, can not be made upon the first visit to a region, or by 

 a single journey through it. The determination of formation limits, and 

 of developmental stages, of aspects, layers, abundance, etc., must necessarily 

 precede, a work which alone takes several years. Moreover, collecting itself 

 requires more than one year in a region containing numerous formations. 

 This is exemplified by the Herbaria Formationmn Coloradcnsnim.^ The 

 preliminary study for this was made from 1896- 1899, the collecting was 

 done chiefly in 1900 and 1901, while additional numbers were added in 

 1902-3. For the purposes of the formation herbarium, specimens should 

 be collected and pressed in such fashion as to show all the ecological fea- 

 tures possible. Plants must be collected both in flower and in fruit, with 

 the underground parts as perfect as may be. Seedlings and rosettes should 

 be included whenever present. In pressmg, one or two leaves should be 

 arranged with the lower ide uppermost to admit of the ready comparison 

 of both surfaces. Opened flowers are valuable for flower biology, while 

 seeds and fruits are desirable for showing migration contrivances. The 

 ferns, mosses, and lichens of the formation should be fully represented, to- 

 gether with the more important fungi and algae. The number of photo- 

 graphs taken for each herbarium should be limited only by considerations 

 of time and expense. The ideal series consists of a general view of each 

 formation, showing its physiographic setting, nearer views of each of its 

 aspects, detail views of its consocies, societies, and layers, and flower portraits 

 of all the constituent species. Such a series can only be obtained by resi- 

 dence through a long term of years, and in most cases general and aspect 

 views, with portraits of the facies and a few of the striking principal 

 species, must suffice. Quadrat and transect charts, together with forma- 

 tional maps, are extremely desirable, and, indeed, all but indispensable. 



245. Arrangement. The arrangement of species within each formation 

 herbarium is based upon the structure of the vegetation. The primary 

 groupings are made with reference to time of appearance and abundance; 

 when definite zones, associations, or layers are present, they must likewise 

 be taken into account. In the Colorado collection, the first division is into 

 three aspects based upon the period of flowering (aspect us vernalis, aesti- 

 valis, autumnalis). Within each aspect, the species are arranged with re- 

 spect to abimdance in the groups, facies, principal species, and secondary 

 species. Each group is placed in an ordinary manila cover, which bears a 

 printed label indicating the aspect and the group. The species labels g.ve, 



^Clements, F. E. and E. S. Herbaria Formationnm Coloradensium. 1903. 



