The Profound Effect on the Structure of Plants 59 



esting to note that while some of the shapes have been named for 

 their resemblance to familiar mathematical forms or common 

 objects (e. g., ovate, lanceolate), the majority have to be desig- 

 nated by combinations of these terms (as ovate-lanceolate, etc.). 



For completion of our subject 

 of leaf shape, one matter of im- 

 portance remains, and that con- 

 cerns the curious emarginations, 

 lobings, and compoundings which 

 so many of the kinds exhibit. 

 The margin of a leaf is typically 

 smooth or entire, and many leaves 

 actually exhibit this character; 

 but others again are more or 

 less waved, toothed, or incised, 

 through the sagging, as it were, 

 of the green tissue between the 

 ends of the veins, or, occasionally, 

 its swelling out beyond them. 

 When this lobing becomes deep, 

 it influences greatly the form of 

 the leaf, especially as it follows 

 the type of the veining. Thus, 

 a deep lobing between palmate 

 veins results in a shape like that 

 of the Ivies, and the ]\Iaples 

 (figure 11, i), while if it goes clear down to the leaf-stalk (in which 

 case the separated segments usually develop little stalks of their 

 own), it results in a leaf that is palmately compounded, like 

 the Woodbine (figure 11, A-). A similar deep lobing in pinnately- 

 veined leaves leads through forms like those of the Oaks to 

 pinnately-compound leaves, like those of the Locust (figure 

 11, I) and many Ferns, which latter, indeed, are often again lobed 

 and compounded, and re-compounded again. In a general way, 



Fig. 15. — Engelmann's Spruce, showing 

 an approximation to the theoretical 

 form of figure 14. (Copied from Kirke- 

 gaard's Practical Handbook of Trees, 

 etc.) 



