PLANT ORGANS AND ORGANISMS 165 



Repand, or Undulate, margin a wavy line. Example: Hama- 

 melis. 



Sinuate, when the margin is more distinctly sinuous than the last. 

 (Stramonium.) 



Incised, cut by sharp, irregular incisions. Example: Hawthorn. 



Run tin ate, the peculiar form of pinna tely incised leaf observed in 

 the Dandelion and some other Composite in which the teeth are 

 recurved. 



A Lobed leaf is one in which the indentations extend toward the 

 mid-rib, or the apex of the petiole, the segments or sinuses, or 

 both, being rounded. Example: Sassafras. 



Cleft is the same as lobed, except that the sinuses are deeper, and 

 commonly acute. Example: Dandelion. 



A Parted leaf is .one in which the incisions extend nearly to the 

 mid-rib or the petiole. Example: Geranium maculatum. 



In the Divided leaf the incisions extend to the mid-rib, or the 

 petiole, but the segments are not stalked. Example: Watercress. 



If the venation is pinnate, the preceding forms may be described 

 as pinnately incised, lobed, parted, or divided. If the venation is 

 radiate, then the terms radiately or palmately lobed, incised, etc., 

 are employed. 



The transition from Simple to Compound Leaves is a very gradual 

 one, so that in many instances it is difficult to determine whether a 

 given form is to be regarded as simple or compound. The number 

 and arrangement of the parts of a compound leaf correspond with 

 the mode of venation, and the same descriptive terms are applied 

 to outline, margin, etc., as in simple leaves. 



Leaves are either pinnately or palmately compounded. The term 

 pinnate is frequently given to the former while that of palmate is 

 often assigned to the latter. They are said to be abruptly pinnate 

 or paripinnate when the leaf is terminated by a pair of leaflets; odd 

 pinnate or imparipinnate when it terminates with a single leaflet. 

 When the leaflets are alternately large and small, the leaf is inter- 

 ruptedly pinnate, as the Potato leaf. When the terminal leaflet is 

 the largest, and the remaining ones diminish in size toward the base 

 the form is known as lyrate, illustrated in the leaf of the Turnip. 



Palmately compound leaves have the leaflets attached to the 



