2 Frederic E. Clements 



mation in detail and with accuracy makes them of much less 

 practical value. 



Formation herbaria are not only invaluable records of vegeta- 

 tion, on account of their lists, quadrat charts, and photographs, 

 but they are also as indispensable to the worker in comparative 

 phytogeography as they are useful in class instruction. When 

 collected with reference to the developmental series and arranged 

 in what may be termed succession herbaria, they will mark a new 

 period in the study of the development of vegetation. For a 

 phytogeographer concerned with the critical comparison of the 

 vegetation of distant countries, such herbaria will put into his 

 hands, at a great saving of time and expense, a much better and 

 more detailed summary of a distant region than he could pos- 

 sibly obtain without actual residence for several years. It is 

 hardly too sweeping to assert that accurate work in the new field 

 of comparative phytogeography can only be done with such 

 means. The value of formation herbaria in class work is evi- 

 dent. On account of the limitations of time and distance, classes 

 can touch but few formations, and these at every other time than 

 at the growing period. For these reasons, an accurate and com- 

 plete formational record that can be consulted or studied at any- 

 time is all but absolutely necessary for class study in the develop- 

 ment and structure of formations. 



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, of 

 aspects, layers, abundance, etc., must necessarily precede, — a work 

 which alone takes several years. Moreover, collecting itself re- 

 quires more than one year in a region containing numerous for- 

 mations. The Herbaria Formationum Color adensium affords an 

 excellent illustration of this. The preliminary study was made 

 from 1896 to 1899; the major part of the collecting was done in 

 1900 and 1 901, while additional numbers were added in 1902-3. 

 Specimens must be taken in both flower and fruit, with the under- 

 ground parts as complete as possible. Opened corollas are valu- 

 able for flower biology, and seeds are highly desirable. In press- 



330 



