THE FLORAL ENVELOPES. 127 



Fig. 33. 



I 



Fig. 33. Thus when the sepals are coherent by their bases as 

 in the Pimpernel a, we employ the terms bi-partite, tri-partite, 

 quadri-partite, according as there are two, three, or four sepals 

 thus united. When the union of the sepals takes place through 

 the lower half N of their margins, such sepals are bi-fid, tri-fid, 

 quadri-fid, as in Erythrsea, b. If the sepals are united with 

 each other by their margins nearly to their summit, they are 

 bi-dentate, tri-dentate, as in Lychnis, c. Finally, if the union of 

 the margins is complete through their entire length, the calyx 

 is said to be entire. It is seldom, however, that the cohesion of 

 the calycine leaves is complete, and the number of lobes at the 

 summit of the calyx will in general show the number of sepals 

 which have cohered together. In the entire monosepalous 

 calyx, the venation assists in determining the number of 

 cohering sepals. 



When the sepals are unequally developed and united, the 

 calyx is said to be irregular. This takes place in the Labiatae, 

 or mint tribe, where some of the sepals of the calyx unite to a 

 greater extent than others, thus forming a bi-labiate or two- 

 lipped calyx, as in the dead nettle, Lamium. (Fig. 34.) The 

 upper lip is composed of three sepals, the lower of two ; the 

 united parts form the tube; the free portions the lobes or 

 segments of the limb; and the part where they join one 

 another the mouth or throat. 



