Chap. II. 



SOLANUM. 



75 



tissue, with lines radiating from the centre. The 

 three groups of vessels, which, though near together, 

 were before distinct, are now completely blended. 

 The upper part of this ring of woody vessels, formed 

 by the prolongation of the horns of the original semi- 

 lunar band, is narrower than the lower part, and 

 slightly less compact. This petiole after clasping the 

 stick had actually become thicker than the stem 

 from which it arose ; and this was chiefly due to the 

 increased thickness of the ring of wood. This ring 

 presented, both in a transverse and longitudinal 

 section, a closely similar structure to that of the 

 stem. It is a singular morphological fact that 

 the petiole should thus acquire a structure almost 

 identically the same with that of the axis ; and it 

 is a still more singular physiological fact that so great 

 a change should have been induced by the mere act 

 of clasping a support.* 



Fumamace^e. Famaria officinalis. It could not 

 have been anticipated that so lowly a plant as this 

 Fumaria should have been a climber. It climbs by 

 the aid of the main and lateral petioles of its com- 

 pound leaves ; and even the much-flattened terminal 



* Dr. Maxwell Masters informs 

 me that in almost all petioles 

 which are cylindrical, such as 

 those bearing peltatu leaves, the 

 woody vessels form a closed rlns; ; 

 semilunar binds of ves-s Is being 

 confined to petioles which are 

 channelled along their upper 



surfaces. In accordance with this 

 statement, it may be observed 

 that the enlarged and clasped 

 petiole of the Solamim, with its 

 closed ring of woody vessels, lias 

 become more cylindrical than it 

 was in its original unclasped 

 condition. 



