Formation and Succession Herbaria 3 



ing, one or two leaves should be arranged with the lower side 

 uppermost to admit of the ready comparison of both surfaces. 

 Seedlings and rosettes should be included whenever present. The 

 number of photographs taken to illustrate each formation 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 associations, groups, and layers, and flower portraits 

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

 by residence through a long term of years, and in most cases, gen- 

 eral and aspect views, with portraits of the facies and a few of 

 the striking principal species, must suffice. For views, a 6}^ x 

 %y 2 inch camera is most satisfactory, while a 4 x 5 is large 

 enough for detail and for individual plants. Quadrat and tran- 

 sect charts are of the greatest value for indicating the minute 

 structure of formations, but the cost of reproduction has proved 

 prohibitive to their use in the Colorado collection. 



As in all formational work, it is difficult to give proper value 

 to the fungi and algae of the various formations. After much 

 deliberation, the writer has decided to treat these, so far as Colo- 

 rado formations are concerned, in a supplementary collection 

 under the title, "Cryptogamae Formationum Coloradensium." 

 This will include the mosses and liverworts as well, the ferns 

 having been treated in the original collection. The plan is to 

 arrange all the cryptogams of each formation in their proper 

 order, grouping them into layers and aspects in so far as possible, 

 and making use of the camera for the detail of groups and the 

 portraits of important species. 



The arrangement of species within each formation herbarium 

 is based upon gross structure when layers and zones are present, 

 and also upon time of appearance and abundance. In the Colo- 

 rado collection, the first division is into three aspects based upon 

 the period of flowering (aspectus vernalis, aestivalis, autunmalis) . 

 Within each aspect, the species are arranged with respect to 

 abundance in the groups, facies, principal species, and secondary 

 species. Each group is placed in a manila cover, bearing a 



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