in 



THE JUNGERMANNIALES 



117 



pears to serve as a reservoir for moisture. These tubular 

 structures sometimes have the opening provided with valves, 

 which open readily inward, but not from the inside, and thus 

 securely entrap small insects and crustaceans which find their 

 way into them. Schiffner ( (i), p. 65) compares them to the 

 pitchers of a Sarraccnia or Darlingtonia, and suggests that 

 they may serve the same purpose. 



The branching of the foliose Jungermanniaceae has been 

 carefully investigated by Leitgeb, and will briefly be stated 

 here. Two distinct forms are present, terminal branching 

 and intercalary. The former 

 has already been referred to, 

 but it shows some variations 

 that may be noted. In most 

 cases the whole of the ventral 

 part of a segment, which or- 

 dinarily would produce the 

 ventral lobe of a leaf, forms 

 the rudiment of the branch, 

 so that the leaf, in whose axil 

 the branch stands, has only 

 the dorsal lobe developed. In 

 the other case, only a part of 

 the cell is devoted to forming 

 the branch, and the rest forms 

 a diminished but evident 

 ventral leaf-lobe, in 

 axil the young branch is situ- 

 ated. The formation of the 

 intercalary branches, which 

 are for the most part of endogenous origin, may be illustrated 

 by Mastigohryum, wdiere the characteristic flagellate branches 

 arise in this manner. The apical cell of the future branch 

 (the branches in this case arise in strictly acropetal order) 

 springs from the ventral segment, and exactly in the middle. 

 It is distinguished by its large size, and is covered by a single 

 layer of cells (Fig. 61). In this cell the first divisions estab- 

 lish the apical cell, wdiich then grows in the usual way. The 

 young bud early separates at the apex from the overlying cells, 

 which rapidly grow, and form a dome-shaped sheath, between 



I „„p Fig. 61. — Mastigobryum trilobatum. Longi- 

 tudinal section of the stem, showing 

 the endogenous origin of the branches; 

 X, the apical cell of the branch, X24S 

 (after Leitgeb). 



