lOO Dr. W. C. Williamson on • 



Type of Lepidodendron brcvifohnu, Williavison, not of 

 Ettinghansen. Sec Schiuipcr, PaUontologie ve'getaky 

 Vol. 2, p. 2. 



Lepidophloios brevifoluni. Will. C, p. jio. 



Terminal twigs extremely slender and very abundant. 

 The smallest about "oS in diameter, including its leaves. 

 Primary xylem strand consisting solely of a few barred 

 tracheids, or with two or three medullary cells in its 

 interior (C.N. 468 to 472). Diameter of the youngest strand, 

 •on of an inch, but soon enlarging into a primary tracheal 

 cylinder with a distinct central medullary cavity occupied 

 by a medulla in C.N. 487. 



Cortex in young twigs of two zones, an outer 

 prosenchymatous one upon which the young leaves are 

 planted, and an inner parenchyma. Twigs frequently 

 dichotomise in a very young state (C.N. 467), when the 

 xylem strand divides into two equal parts, each one soon 

 developing into a distinct cylinder surrounding a medullary 

 cavity. In more advanced growths, but yet comparatively 

 early, an exogenous secondary xylem strand encloses the 

 primary one. In my largest section this strand attains to 

 a diameter of i'3 of an inch, the central medulla being here 

 *5 broad. These larger branches are rare, and in what we 

 possess all the cortical tissues internal to the prosenchy- 

 matous zones have disappeared. The medullary cells in 

 such branches are in vertical rows, and their leaves approach 

 those of LcpidopJdoios. In one specimen (C.N. 502), the 

 secondary xylem strand is detaching a complete segment 

 to become a strand of the Halonial type. 



Young Twigs. Axial Tissues. 

 Medullary Cavity. 



C— p. 284, Fig. 2. See C.N. 466, 467, and 469, and little, if any, 

 parenchyma existing. 



C— p. 284, Fig. I and 3, C.N. 468. 



C— p. 285, Fig. 4. See C.N. 479. 



C— p. 286, Fig. 8, C.N. 917. 



