TOOTHWORT. 201 



being divided into three dentate lobes, making what is called a 

 compound leaf. 



331. Parts of the flower. — The flowers are several, and they 

 are borne on quite long stalks (pedicels) scattered over the 

 terminal portion of the stem. We should now examine the 

 parts of the flower, beginning with the calyx. This we can see, 

 looking at the under side of some of the flowers, possesses four 

 scale-like sepals, which easily fall away after the opening of the 

 flower. They do not resemble leaves so much as the sepals of 

 trillium, but they belong to the leaf series, and there are two 

 pairs in the set of four. The corolla also possesses four petals, 

 which are more expanded than the sepals and are whitish in 

 color. The stamens are six in number, one pair lower than 

 the others, and also shorter. The filament is long in propor- 

 tion to the anther, the latter consisting of two lobes or sacs, 

 instead of four as in trillium. The pistil is composed of two 

 carpels, or leaves fused together. So we find in the case of the 

 pepper root that the parts of the flower are in twos, or multiples 

 of two. Thus they agree in this respect with the leaves ; and 

 while we do not see such a strong resemblance between the 

 parts of the flower here and the leaves, yet from the presence 

 of the pollen (microspores) in the anther sacs (microsporangia) 

 and of ovules (macrosporangia) on the margins of each half of 

 the pistil, we are, from our previous studies, able to recognize 

 here that all the members of the flower belong to the leaf 

 series. 



332. In trillium and in the pepper root we have seen that 

 the parts of the flower in each apparent whorl are either of the 

 same number as the leaves in a whorl, or some multiple of that 

 number. This is true of a large number of other plants, but it 

 is not true of all. The trillium and the dentaria were selected 

 as being good examples to study first, to make it very clear 

 that tlie members of the flower are fundamentally leaf structures, 

 or rather that they belong to the same series. of members as do 

 the leaves of the plant. 



