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THE AMERICAN NATURALIST. [Vol. XXXVI 11. 



in transverse section to stand out from the general line of the 

 epithelium and lie within the cavity proi^er. More rarely such 

 cells are so multiplied as to fill the entire cavity, and they may 

 themselves be filled with granular resin. Such features are 



clearly defined (Fig. 45), and it is evident from the way in 

 which such cells originate from the epithelial cells that they are 

 •»f the nature of thyloses. A longitudinal section through such 

 a reservoir (Fig. 46) shows how such thyloses occupy the entire 

 ^■:i\ity of the cyst, while in other cases they may be purely 

 I'h;i1 (l ig. 44). Among fossil sequoias similar thyloses form a 

 most characteristic feature in the resin passages of the medullary 



'aroliniana there are no secretory reservoirs, but 

 ;ii)n between the spring and summer wood of the 

 l ing there are peculiar aggregates of resin cells of 



rounded (jutline but forming a continuous series 

 e extent. An analysis of these aggregates shows 

 "mi),,sed of thick-walled and rounded resin cells, 



there may be a small central intercellular space 

 efinite organization of epithelium. In such aggre- 



