2 ELEMENTS OF STRUCTURAL BOTANt. 



CHAPTER IV. 



EXAMINATION OF OTHER COMMON PLANTS WITH HYPOGY 

 NOUS STAMENS SHEPHERD'S PURSE ROUND- 

 LEAVED MALLOW. 



28. We shall now proceed to examine some plants, 

 the flowers of which exhibit, in their structure, impor- 

 tant variations from the Buttercup, Hepatica, and 

 Marsh-Marigold. 



Shepherd's Purse. This plant (Fig. 26) is one of 

 the commonest of weeds. As in the Buttercup, the 

 foliage-leaves are of two kinds, radical and cauline, the 

 former being in a cluster around the base of the stem. 

 The cauline leaves are all sessile, and each of them, at 

 its base, projects backward on each side of the stem, so 

 that the leaf somewhat resembles the head of an arrow. 

 Such leaves are, in fact, said to be sagittate, or arrow- 

 shaped. The flowers grow in a cluster at the top of the 

 stem, and, as the season advances, the peduncle gradu- 

 ally elongates, until, at the close of the summer, it forms 

 perhaps half of the entire length of the stem. You will 

 observe in this plant, that each separate flower is raised 

 on a little stalk of its own. Each of these little stalks 

 is a pedicel, and when pedicels are present, 

 the term peduncle is applied to the por- 

 tion of stem which supports the whole 

 cluster. 



29. The flowers (Fig. 27) are rather small, 

 and so will require more than ordinary care 

 in their examination. The calyx is polysepalous, and of 



Fig. 27. Flower of Shepherd's Purse, enlarged. 



