STIPULES AND lENDKItS. 



21 



Held between the eye and the light, leaves sometimes appear 

 pricked full of little holes, such as a needle would make. These are 

 minute receptacles of oil, rendering the leaf transparent in those 

 places. Leaves where they occur are said to be " dotted." 



In many families of plants there are appendages to the leaves, the 

 presence of which frequently helps much to the discrimination of 

 them. Two principal kinds are observable, called respectively 

 " stipules " and " tendrils." 



Stipules resemble a pair of little wings, growing one upon each 

 side of the petiole. Sometimes they are enormous in proportion to 

 the leaf, as in the pansy and the culinary pea ; and sometimes they 

 are reduced to mere thorns, as in the Robinia. Fig. 49 shews their 

 form in the rose-leaf. 



Fiff. 46. 



Fig. 48. Fig. 49. 



Tendrils are those beautiful little twining green fingers which we 

 see upon such leaves as those of the pea, enabling it to grasp a 

 friendly neighbouring prop, and ascend into the air. They are either 

 simple or branched. Tendrils, however, are not always attached to 

 leaves, being sometimes modifications of other organs. 



Finally, there is the position of the leaves upon the stem, a circum- 

 stance always of great moment. We find them either growing in 

 pairs, each leaf pointing in a contrary direction, when they are called 

 "opposite;" (Fig. 47.) or singly, when they are "alternate;" (Fig. 46.) 

 or in a ring, like the spokes of a wheel, when they are called " whorled " 

 or " verticillate." (Fig. 48.) If alternate leaves are distributed irregularly 

 Over the stem, they are said to be " scattered; " and when opposite 

 ones are very close together, and pressed close against the stem, so as 



