748 METASPERMAE OF THE MINNESOTA VALLEY. 
discussed. It will be observed that the marsh and swamp ele- 
ment forms a percentage of the Metachlamydeae exactly 
equivalent to the similar percentage of the Archichlamydeae. 
In this case the explanation may be that the younger group of 
the Metachlamydeae furnishes so large a percentage of this 
element, comparatively, because the influence of the tensions 
is such that in a younger group many weaker plants will be 
forced into the morassic habitat. It is apparent that either the 
plants of new and variable type or the plants of an older and 
less plastic type will be less competent to struggle for the op- 
timum habitat than a group of plants neither too modern nor 
too ancient. In the marsh and swamp percentages of the 
modern valley may therefore be read a word or two concerning 
those long-past ages when the Archichlamydeae in turn were 
similarly conditioned in their relations with the conifers of the 
old Cretaceous flora. 
It will be interesting to examine the ranges in the continent 
of these two groups of physiognomic elements. Tabulations 
are readily compiled from Tables G, H, Jand K. The follow- 
ing tabulation will serve to indicate ina general way the range 
peculiarities of the habit-elements: 
TREES, SHRUBS HERBS 
g/ 8} g1als g/l} ¢ 
g/o/$ ei fig shes 
S| Pls SIPs SIEls 
38. Ranoe-Staristics or THE |'§ | 2 & Sigal S| 2] 
HABIT-ELEMENTS. ee Asean | ed slalé oe) a 
Bialst jelsls Ble\a 
a|3/'3 a/3/13 alsil's 
s(erslsislelslslsielsls 
Sia l/Slelel/<a/Selaelai<a/seiea 
Northern species 0 | 20) 2/2270 |51 {21 |72 | 226) 186] 136] 568 
Southern species...................{ 0] 41] 6] 47]2 |47 {10 [59 |) 227] 256] 303] 786 
Eastern species......................{ 0] 46) 7 | 53] 2 |67 {25 |94 || 308] 283] 284] 875 
Western species........... .-....06+ 0/13] 2) 1510 [34 118 (52 | 176} 182} 178) 536 
Per cent. of all northern........... 0 /90.9 Beta 0 |70.6 ued oe 39.77/32. 7/27 .6|100, 
Per cent. of all southern..... ..... 0 |87.2 18:8 109 4.4 179.5 ae 28 .8/32,5)/38. 7/100. 
Per cent. of all eastern............. 0 |86.7 tg 2.3 171.2 ees 34 ,1/32.3]/33.6]100. 
Per cent. of all western............. 0 |86.3/13.7 100 || 0 [65.3 mele 32.8/33.9}33.3]100. 
t 
Northern per cent. of each......... 0 |41.6 tas aa 0 68.0 itd aan 68 .2/54.'7|39.3/55.8 
Southern per cent. of each......... 0 |85.4/95.'7 85.4/100./62.6 ee i ie 75 2187 5/772 
Eastern per cent. of each...........] 0 |95.8 1G. 0:8 100. |39.3/92.6 ieee ee 83 .2/82.0/86.0 
Western per cent. of each...........| 0 |27.0)29.5 27.21 0 |45.3 ee 53.5/51.4|52.7 
Total spectes........0606. cece 0/48] 7| 55/2 |z5 lor l1os ls 340) 246) 1017 
