IV 



THE JUNGERMANNIACE^E 



III 



apical cell a short leafy branch, bearing the sexual organs, is 

 produced.^ 



Considerable variety is exhibited by the leaves of the 

 Acrogynae as to their form and position, but all agree in their 

 essential structure and early growth. The two lobes may be 

 either equal in size or unequal. In the latter case either the 

 dorsal or ventral lobe may be the larger, when the leaves are 

 overlapping, as occurs in most genera. Where the dorsal half 

 is the larger it covers the ventral lobe of the leaf in front of it, 

 and the leaves are said to be " incubous " ; where the reverse is 

 the case, the leaves are " suc- 

 cubous." These differences 

 are of some importance in 

 classification. 



In many species, especi- 

 ally the tropical epiphytic 

 forms, one lobe of the leaf 

 frequently forms a sac - like 

 organ, which appears to serve 

 as a reservoir for moisture. 

 These tubular structures some- 

 times have the opening pro- 

 vided with valves, which open 

 readily inward, but not from 

 the inside, and thus securely 

 entrap small insects and crus- 

 taceans which find their way 

 into them. Schiffner ^ com- 

 pares them to the pitchers of 

 a Sarracenia 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 inter- 

 calary. 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 ordinarily would produce 

 the ventral lobe of a leaf, forms the rudiment of the branch, so 



Fig. 53- — Mastigobryiun irilohaUtm (Nees). 

 Longitudinal section of the stem, showing the 

 endogenous origin of the branches ; .r, the 

 apical cell of the branch, X 245 (after Leitgeb). 



1 For a complete account of these forms as well as others, see Goebel's papers in 

 the Annals of the Bidtcnzoj-g Botanical Garden, vols. vii. and ix., and in Flora, 

 1889 and 1893. 



- Schiffner (i), p. 65. 



