590 MESOZOIC FLORAS OF UNITED STATES. 



ANALYSIS OF THE TABLE. 



It will be seen by this table that the whole number of species and 

 varieties or plant forms which have been collected since the appearance of 

 Professor Fontaine's monograph, and which he has treated in the above 

 paper, is 176. As regards their diagnostic value in determining age and 

 correlating the beds, he gives great weight to their relative abundance, and 

 in preparing his report he took pains in most cases to count the specimens 

 and give the exact number represented for each species. But where there 

 were many specimens of one species he contented himself by so stating, 

 without an exact count. After completing and submitting his report he 

 shipped the entire collection to Washington. In editing his report for this 

 paper I found it essential to consult the material constantly in order to 

 make the history of the numerous collections complete and to indicate the 

 exact source, proprietorship, and destination of every specimen, dupli- 

 cates as well as figured types. This required me to arrange the specimens 

 primarily by localities and then by species from each locahty. Having 

 done this it was comparatively easy to make an exact count of all the 

 specimens of each species from each locality. As every determinable 

 specimen was labeled both for the locality and for the species, this could 

 readily be done, although, on account of the size of the aggregate collec- 

 tions, the task was laborious and required much time. In most cases the 

 counting amounted simply to a verification of Professor Fontaine's manu- 

 script, but in a number of cases, as might naturally be expected, the 

 two counts differed. In all such cases I have used my own final count 

 instead of his. The discrepancies were sometimes found to be due to the 

 accidental mixing of specimens from different localities where the mate- 

 rial was very similar, as, for example, that of Langdon with that of Tip 

 Top, where one of the figured types was involved. 



In making the count I extended it to all the species, no matter how 

 numerous the specimens, even including Cladophlebis acuta from the 

 Arlington beds with exactly 400 specimens. These exact results are sub- 

 stituted in the descriptions of the localities for the general statements 

 which Professor Fontaine regarded as sufficient. 



The table of distribution now under consideration differs from the 

 usual form by taking account of the number of specimens as well as the 

 mere fact of their occurrence at the several localities. Where, from 



