ON LEAVES. 



485 



I would venture, then, to suggest these considerations as throwing 

 light on the reason why herbaceous plants so often have their leaves 

 much cut up.* 



Next let me say a few words on the reasons why some plants have 

 broad and some narrow leaves. Both are often found within the 

 limits of a single genus. I have ventured to indicate the distance 

 between the buds as a possible reason in certain cases. It would not, 

 however, apply to herbaceous genera such as Plantago or Drosera. 

 Now, Drosera rotundifolia (Fig. 25) has the leaves nearly orbicular, 



Fig. 25. 



Fig. 26. 



vhile in D. anglica (Fig. 26) they are long and narrow. Plantago 

 media (Fig. 27) has ovate leaves, while in P. lanceolata (Fig. 28) they 

 are lanceolate, and in P. maritima nearly linear. More or less similar 

 cases occur in Ranunculus. 



These differences depend, I believe, on the attitude of the leaf, for 

 it will be found that the broad-leaved ones are horizontal, forming a 

 rosette more or less like that of a daisy, while the species with nar- 

 rower leaves carry them more or less erect. In the daisy the rosette 

 lies on the ground, but in other cases, as in Daphne (Fig. 29), it is at 

 the end of a branch. 



Any one who has looked with an observant eye at the vegetation 

 of hot, dry countries must have noticed how much the general char- 

 acter of the vegetation differs from that which prevails in a climate 

 like ours. There is a marked increase of prickly, leathery, and aromatic 

 species. The first two characteristics evidently tend to protect the 

 leaves. As regards the third, Mr. Taylor, f in his charming book on 



* Mr. Grant Allen, who had been also struck by the fact that herbaceous plants so 

 often have their leaves much cut up, has suggested a different explanation, and thinks it 

 is due to " the fierce competition that goes on for the carbon of the air between the 

 small matted undergrowth of every thicket and hedge-row." 



f Page 311. 



