STATISTICS OF METASPERMAE. 751 



necessity of explaining such a fact by the tension-lines and the 

 law of ejections, and reciprocally the fact of distribution is of 

 value as evidence of the soundness of the law. 



The marsh-plants exceed the total flora in northernness 

 easternness and westernness, but fall behind in southernness. 

 Not yet fully distributed as are the aquatics, they indicate bet- 

 ter the influence of the continental tension. Marsh plants in a 

 given region of the northern hemisphere may be expected to 

 present distal rather than central characters, for as has been 

 discussed above, the tendency to adopt the morassic habitat is 

 a distal or tension-line phenomenon. As might be expected 

 where different forces are acting to determine the percentages 

 one will often partly neutralise another. It is seen, for exam- 

 ple, in the table, that the northern and southern percentages of 

 the metachlamydeous marsh-plants are very close together, 

 while the eastern and western percentages are not so close. 

 This is just the reverse of the condition among the Metachla- 

 mydeae as a group, in the Minnesota- valley flora, and indicates 

 the selective influence of habitat upon range. In the drier-soil 

 element, on the other hand, the condition of the total flora re- 

 appears and is accentuated. 



The drier -soil plants lead the total flora only in southernness, 

 while in northernness, easternness and westernness they fall 

 behind. Of the element, the Archichlamydeae lead in northern- 

 ness, the Metachlamydeae in southernness, the Monocotyle- 

 dones in easternness and the Metachlamydeae in westernness. 

 The Archichlamydeae of the drier- soil are less northern, more 

 southern, less eastern and less western than in the total ele- 

 ment. The Metachlamydeae of the drier-soil are less northern 

 more southern, less eastern and less western than in the total 

 element. The Monocotyledones do not differ from the two 

 groups mentioned, in this particular. That both the eastern- 

 ness and westernness of the drier-soil element should be de- 

 creased in all taxonomic groups indicates the wide east and 

 west distribution of the two elements the removal of which 

 leaves it as the residuum. 



In general the study of the tables which indicate the range 

 of the physiognomic elements will add weight to the belief that 

 the three taxonomic groups are of different and distinct mean- 

 ing in the distribution. Space scarcely permits as exhaustive 

 an analysis as might be useful but enough has been noted in pass- 

 ing to show how a further and more complete analysis should 

 properly proceed. Careful examination of the tables and com- 



