EVOLUTIONARY PRINCIPLES OF THE COMPOSITAE 441 



involucral scales. Certain dark dots on the superior margin of 

 the upper bundles indicate the presence of oil canals. Structures 

 of this nature are entirely lacking in the axial bundles and in the 

 traces which have only recently left the cylinder of the stem. 

 Fig. 305 will serve to demonstrate the truth of the statement 

 just made. In a is shown a strand near the axial region which 

 obviously is not characterized by the presence of oil canals. In 

 b, on the contrary, representing a trace destined to an involucral 



FIG. 305. a, axial strand of infloresence of C. Scolymus; b, a strand of an invo- 

 lucral scale in the same. 



scale, a series of somewhat imperfectly developed oil canals appears 

 along the upper margin. 



The Cynareae represent a transition anatomically from the 

 Tubuliflorae to the Liguliflorae. In the Cichoriae, on the other 

 hand, we have to do with very typical representatives of the 

 Liguliflorae, since in this subfamily all the florets are strap-shaped 

 and the secretion is milky in its nature and contained in the region 

 of the phloem. Interestingly enough in the oyster plant (Trago- 

 pogoti] and in the salsifies (Scorzonera and Scolymus) vestiges of 



