442 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



of which rootlets are given off, which perforate the scales with 

 which it, as well as the rest of the surface, is often clothed, 

 exactly as the scales of bulbs, or the bases of the leaves, are 

 perforated by the adventitious roots in many monocotyledons. 

 The species vary in the breadth and thickness of the fronds, 

 the scaliness, the length of the peduncles, the size and division 

 of the receptacles, the number of the fruit, and other points. AH 

 the widely diffused species exhibit a number of forms, which 

 are in general easily referable to their respective types. 

 The fruit is developed with more certainty where the rays of 

 the sun have access ; in the shade the frond is covered with 

 gemmiferous cups. Both, however, grow occasionally together 

 on the same frond. 



3. LuNULARi^, Nees. 



Sporangia seated on a common peduncle, each surrounded 

 by a proper involucre, and sphtting into four or eight valves, 

 or irregularly torn. 



487. This small tribe, like Targioniew, consists of but two 

 genera, characterised by the sporangia being at once seated on 

 the top of the common peduncle without any distinct recep- 

 tacle. An approach to this structure was already made in 

 Fegatella, through which, by means of Plagiochasma and 

 Lunularia, a direct transition is made to Jungermanniacece. 

 The latter genus is found in several parts of Europe, including 

 Great Britain and Ireland. It extends, however, to the 

 Canaries and Azores, and is found again in ChUi ; the former 

 appears under a single species in Corcyra, the other rather 

 numerous species occurring principally in warm countries, and 

 like many other sub-tropical forms, is found in New Zealand. 

 In Plagiochasma (Fig. 93, a) there is a slight attempt at a 

 receptacle, each lobe of which is transformed more or less into 

 a vertical bivalved involucre, which bears at its base a shortly 

 pedicellate sporangium, which bursts irregularly. It is divisible 

 into two sections, of which one forms innovations at the tips, 

 the other from the ventral side of the frond. The male fruit is 

 in sessUe lobed stellate or entire discs on the same or in different 

 individuals. In Lunularia (Fig. 93, d), which derives its 



