THE COMPOUND LEAF. 



101 



CHAPTER XXII. 



THE COMPOUND LEAF, ETC. 



300. If we conceive of a simple leaf becoming a compound 

 one, on the principle of " deficiency of tissue between the veins," 

 it will be evident that the same forms of venation are represented 

 by the branching petioles of the latter as by the veins of the 

 former. The number and arrangement of the parts will there- 

 fore in like manner correspond with the mode of venation. 



301. The divisions of a compound leaf are called leaflets and 

 the same distinction of outline, margin, etc., occur in them as in 

 simple leaves. The petiolules of the leaflets may or may not be 

 articulated to the main petiole, or rachis^ as it is called. 



354 



358 356 



S55 



Compound leave*. 354, Trifolium repens. 355, Destnodium rotundifolium. 356, Sesbania. 357, Cas- 

 sia. 358, Agrimonia. 



302. Pinnately compound. From the pinnate-veined ar- 

 rangement we may have the pinnate leaf, where the petiole 

 (midvein) bears a row of leaflets on each side, either sessile or 

 petiolulate, generally equal in number and opposite. It is un- 

 equally pinnate (357) when the rachis bears an odd terminal 

 leaflet, and equally pinnate (356) when there is no terminal 



