GEOLOGICAL OBSERVATIONS 



Specimens from Medial Moraine, December 11, 1908 



(No. 101) 



" Longitudinal sections of the included dark masses 

 give a homogeneous banded appearance of a distinctly 

 organic nature. The banded appearance is due to the 

 vascular nature of the organic elements composing the 

 mass. The whole structure recalls to one's mind the 

 appearance given by longitudinal sections of the xylem 

 portion of the vascular area of a gymnosperm, such as 

 Pinus. Only the xylem area is represented in the speci- 

 men, no traces of medullary, cortical, or phloem tissue 

 being visible. Medullary rays are present as shown in 

 the micro-photograph. 



" The xylem itself is composed of a homogeneous mass 

 of vessels, tracheidal in nature, no differentiation as re- 

 gards the vascular elements being present. In places one 

 m.ay readily make out in longitudinal sections dark opaque 

 bands of much greater size individually than the tracheides. 

 These in all probability represent resin passages belong- 

 ing to the xylem. It would seem, further, that these 

 masses might be considered as being nothing more than 

 an aggregation of material similar in nature to that of 

 the walls, and due to changes under the process of petri- 

 faction. This, however, is opposed by the fact that they 

 occur even in these small sections fairly commonly, and 

 at the same time are all of exactly the same size as regards 

 width. At all events they represent some definite struc- 

 ture, and in all probability resin passages. 



" The walls of the tracheids themselves seen under 

 the high power of the microscope appear to be pitted, 

 but the preservation is by no means good enough to war- 

 rant any remarks on this beyond that in the common 

 wall of adjacent tracheides occur clear spaces of the same 

 relative importance as the bordered pits of such a 



315 



