224 FLOKA OF LOWEE COAL MEASUEES OF MISSOURI. 



part iu pi-eserving the roundish, distinct outHne of the boss seen in the 

 impressions earher described. It must be remembered that on the cortex 

 of the stems the interior surface of the large bosses is shghtly concave. A 

 resemblance to the impressions is seen in several of the bolsters in the abraded 

 and parti}' decorticated portion on the right in the tigure. There is, how- 

 ever, when the entire cortex is preserved, no line of displacement or break 

 in the continuit}' of the epidermis beyond the leaf scar along this large sub- 

 circular or subtriangular boss that, in my judgment, can be construed as 

 marking the separation of any appendage or organ. 



Proceeding to the observation of the characters above and within the 

 angle of the leaf scar, we note, as seen in the photographic enlargement, 

 PI. LXVIIl, Fig. 1, an oval or slightly ovate area, the vertical diameter of 

 which is about 2.5 ram., the transverse diameter being about 1.75 mm. The 

 surface of this o^-al area is slightly raised as a boss above the concave sur- 

 face within the large convex, rounded boss, and is bordered in many cases by a 

 ver}^ narrow, low, and sometimes obscure rim, or by a narrow adjacent fur- 

 row. One or both of these conditions are possibly merely the result of pres- 

 sure on the surface of the smaller, oval boss, since there is occasionally seen 

 hardly more than the sharply defined change of level in passing- across its 

 margin down to the large boss. I am inclined, however, to regard the nar- 

 row bordering rim, which is generally present, as normal. The lower end of 

 this oval rim appears to become nearly contiguous to if not actually united 

 with the leaf scar; and at the lowest point it seems, in a few bolsters, to die 

 ou-t below, and partly inclosing, a small punctiform mammilla, which, in one 

 instance, it appears to completely inclose. It is possible that this mammilla, 

 which is in many cases discernible, should be regarded as belonging to the 

 vascular trace of the leaf; but in the specimens before me it seems to be 

 distinct from the leaf, if n(it, in fact, separated therefrom by a continuation 

 of the oval rim. Within the oval boss just described is a small concave 

 oval area, which is sometimes obscure in the lower part. This depression, 

 the margin of which is nearly parallel to the outer border of the oval boss, 

 the distance between being- l)ut little more than .5 mm., is deepest near the 

 upper end, where it surroiuids a minute bordered pit or umbilicate trace. 

 The latter is the "trace" observed iu the central area of the impressions and 

 decorticated stems first described. The true vascular trace of the leaf is 



