FLOIIA OF 'I'liK KOOTAXIK FORMATION. 305 



tij) when iiiulistortod, hut ot'tcMi from pi'cssurc hcconio iiai'i'owcf at their 

 oiids. Distortion from pi-cssuro often causes t!ie se<i'meiits to incline 

 towai'd the ends of the leaf, and thus tliey seem to i^o off at an an^ie 

 smallei' than the noi-mal one with the midi'il). Tliey are attached by 

 the (Mitire \vi(hh of theii' bases to tlie uppei' face of the midiili of the leaf. 

 so tluit the adjacent bases of the opposit(> sesiments aic separated by a 

 raised line. There is some indication that with a^e they become more 

 loosely attached to the midi'ib. .\t any i-ate the (Jevsei- specimens show 

 numerous detached segments that have separated fi-om the midrib along 

 this line. Detached segments are much more common than those borne 

 on the midi'ib. This deciduous character is marked in the (Jeyser fossils, 

 but is not uottHl by previous descril)ei's of this fossil. The frequent 

 detachment of the segments does not seem due solely to the accidents 

 of preserwition. The width of the segments varies gi'(>atly, for some 

 leaves have only two segments on a side and others hav(> th(> lamina on 

 each side of the midrib dividefl into muiierous segments that are very 

 uniform in size and shape. Others have numerous segments, but they 

 \-ary greatly in width. In some cases the apparent segmentation, as 

 well as the shape, is due to pressure, the lamina splitting on the yielding 

 of the rock material. The width of the segments can not then be regarded 

 as a feature of any importance, and the same may be said of the number 

 of nerves, for that varies wdth the width of the segments. 



The nerves, although slender, are remarkably distinct. They are 

 always single, and when the segment is not distorted by pressure they 

 are sliictly parallel. The pressure, however, has frequently narrowed 

 and sharpened the ends of the segments, and then the ner\'es are crowded 

 in the distorted portion. The nerves are described by previous observers 

 as going off at right angles with the midrib, whereas in the Geyser fossils 

 they rarely do so, but more commonly make an angle somewhat smaller. 

 In some of the figures given by Schenk they are represented as making 

 a much smaller angle. The nerves in their course to the ends of the 

 segments make a slightly sigmoid flexure, so that tlieir tips are directed 

 slightly forward. In the leaves distorted by pressure in the way men- 

 tioned before, this forward inclination is exaggerated. The nerves are 

 thickened at the insertion of the segments on the midril) and the pressure 

 sometimes causes them to appear as raised lines on the surface of the 



Mos xi.viiT — 0.5 20 



