TRILLIUM. 199 



of trillium belong to the leaf series we could obtain evidence 

 from the transformations which the flower of trillium sometimes 

 presents. In fig. 178 is a sketch of a flower of trillium, made 

 from a photograph. One set of the stamens has expanded into 

 petal-like organs, with the anther sacs on the margin. In fig. 

 177 is shown a plant of Trillium grandiflorum in which the 

 pistil has separated into three distinct and expanded leaf-like 

 structures, all green except portions of the margin. 



Exercise 62. 



328. Toothwort (dentaria). Note the general habit of the plant ; the 

 rather long, slender, smooth, fleshy, underground, perennial root stock 

 (stem) ; the rudimentary leaves ; the roots ; the growing end some distance 

 ahead of the point where the annual flowering shoot arises ; compare with 

 trillium in this respect. 



The flowering annual shoot ; note the slender, smooth stem, the two 

 opposite leaves which are three divided (trifoliate), the open raceme of 

 flowers terminating the shoot. 



Exercise 63. 



329. The flower. Compare the parts of the flower with the leaves. The 

 flowers should be collected before all of them are open, since the sepals fall 

 away quite easily. Note that the flower parts are in twos or multiples of 

 two, while in trillium the parts are in threes or multiples of three. In each 

 case the number of parts in a whorl is the same as the number of leaves in a 

 whorl, so that this strengthens the view of the parts of the flower being 

 homologous with the leaves. 



Illustrate and describe the different members of the flower. The pistil 

 here is also a compound pistil. 



If there is time compare with other flowers like the toothwort, as the 

 shepherd's purse, mustard, etc. 



DESCRIPTION OF THE TOOTHWORT. 



330, General appearance. For another study we may take 

 a plant which belongs to another division of the higher plants, 

 the common "pepper root," or "toothwort" (Dentaria di- 

 phylla) as it is sometimes called. This plant occurs in moist 



