Nos. 455-456.] COMMON ROADSIDE PLANTS. 



831 



produced and in the mature condition the leaves have four pairs, 

 as in Fig. 45, which represents the typical leaf of the species. 



Leaves like that shown in Fig. 45 are produced until the time 

 of flowering. Then a reduction in the num- 

 ber of teeth takes place. Leaves with four, 

 then three, pairs of lateral teeth are produced 

 and nearer the flower heads, leaves with two 

 pairs are shown in Fig. 46, later with the 

 single pair (Fig. 47), and finally below the 

 flower, the simple leaf shown in Figure 48. ttagtsln'the bcaT- 

 The reduction here is carried on in a definite ized senescence beiow the 

 manner and retraces exactly, in reversed ^\,oJ^'"Z'\Li 

 order, the same stages that are passed stage in the reduction, 

 through in the early spring growth, so that, using numbers for 

 the lateral teeth, we may represent the stages graphically, call- 

 ing the entire leaf number i, as follows : 



Early spring growth to Flowering 



3, 5, 



7, 5, 3, 



Eiipatoritivi perfoliatum L. 

 (Thorough wort. Boneset.) 



This well known plant shows in its leaf characters certain 

 things which may be noted here as in the same line with the 

 preceding cases. The main leaf character of this plant is the 

 connate-perfoliate form of the leaf. This, however, by an exam- 

 ination of a flowering specimen, will be seen to occur on only a 

 part of the stem. In the early spring growth of the plant, the 

 bases of the opposite leaves are free and narrow. Later the 

 coalescent form is taken on and kept until well toward the flow- 

 ering. Then the early form is again taken on, the base of the 

 leaves being narrowed and failing to meet. 



A variety of this species, var. cuncahnn Engel., is apparently 

 a more primitive form. It keeps the early character throughout 

 Its life history, the leaves failing to coalesce at their bases. 

 This variety also has fewer flowered heads than the typical form 

 of the species. 



