1 86 THE PLANT WORLD. 



the perianth into an ascending- or upright position. The leaves on 

 this branch (of which there are only three or four pairs) are prac- 

 tically all modified into bracts. Those at the base are very small, 

 but they rapidly increase in size toward the perianth until the 

 uppermost ones are often i.s"^'"- long and i™™- wide. These upper- 

 most bracts are ovate in shape, very blunt at the apex and cut for a 

 short distance into four to six small, sharp teeth ; their margins are 

 usually entire, but sometimes bear an indistinct tooth or two on the 

 sides. The bracteoles also increase in size toward the perianth, and 

 the uppermost is nearly as large as the corresponding bracts and 

 scarcely different from them in shape. There is no adherence be- 

 tween bracts and bracteoles. Both of these structures are built up of 

 cells much larger than the leaf -cells and with more thickened walls, 

 the latter however, showing little or no indication of trigones. 



The perianth is three-lceeled in the upper part, but the keels, in- 

 stead of being alternate with the bracts and bracteoles, are opposite 

 them, and the perianth therefore presents a different type of structure 

 from that found in Lophocolea. Assuming as before that this peculiar 

 / \ organ is built up of two side-leaves and an under- 



' \ leaf, which retain their proper relative positions, it 



I ^ \\ is clear that each of these leaves is folded length- 



I S" %\ wise through the middle and that the keels of the 



/ \ perianth represent the folds of the leaves and not 



their united edges, as was the case in Lophocolea. 



Under-leaf. ^, r ^ . , 



These two types of structure are of considerable 



^'^^- ^- systematic importance, and are constant through- 



out large groups of genera. The type found in LopJiocolea., which is 



perhaps the more primitive of the two, is called 



" epigonianthous," because the third keel is le 



turned away from the ground; while that found \ 

 in Lepidozia is called " hypogonianthous" because 

 the third keel is tvirned toward the ground. In 

 the accompanying figures, i represents the dia- 

 grammatic cross-section of an epigonianthous 

 perianth, and 2, that of a hypogonianthous peri- ^'^^' ^* 



anth. It may be added that the perianth of Lepidozia is slightly curved 

 and fleshy, and that it is composed of two layers of large thick-walled 

 cells throughout the greater part of its extent. At the mouth it is 

 contracted and very minutely denticulate, the teeth being usually 

 little more than slight projections from the marginal cells. 



Yale University. 



