A crogynous J unger manniales. 
27 3 
runs forwards and downwards, and the fore edge of the leaf is 
overlapped by the hinder edge of the next leaf in front—this is the 
succubous arrangement (Fig. 45, A. B). If the growth of the stem is 
epitropic (greater on the upper side), we get the reverse or incubous 
arrangement (Fig. 45, C; Fig. 46). 
A 
Fig. 46. Leaf-pitchers of Frullania, as seen on ventral side of the shoot 
of (A) F. tamarisci and (B) F. dilatata. 
Taking first the forms in which the leaf is flattened in one plane, 
the insertion being a straight or slightly curved line, we find every 
transition between leaves which are entire or very slightly notched 
and those which are divided to the base into two or more lobes. 
With this type of insertion, which may be either succubous or 
incubous, the lobes in the case of notched or divided leaves are 
usually equal in size. The form of the leaf is, however, often 
complicated when the lobing is accompanied by folding, each lobe 
being attached independently to the stem and the two lines of 
attachment meeting at an angle which is often very sharp, while 
the leaf itself shows a more or less acute fold or keel. In these 
“ complicate-bilobed ” leaves the lobes may be about equal in size 
(e.g., Marsupella, some species of Scapania) and the leaf is neither 
incubous nor succubous. But in most cases the lobes of the 
complicate leaf are unequal in size, the dorsal lobe being the larger 
as a rule and the leaf arrangement incubous (e.g., Radula , Porella, 
