^90 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



reproductive, such a junction is not uncommon, without taking 

 into account any pycnidiiform fruit. We shall have httie 

 hesitation, therefore, in cutting off, as autonomous plants, all 

 such productions as Pyrenothew, in which no asci have at pre- 

 sent been detected. They are, in fact, due to mere pycnidia of 

 so many Verrucarice. 



1. LiMBORIEI, Fr. 



Excipulum carbonaceous, at length opening by means of an 

 irregular pore. Thallus crustaceous, epiphyllous, originally 

 sub-epidermic. 



429. Omitting such plants as those mentioned in the pre- 

 ceding paragragh, we first encounter those species with a true 

 crust, which, in some cases, approach near to Fungi, and are 

 mostly parasitic on living leaves. It has been stated before, 

 that such genera as Strigula are at first developed beneath 

 the true cuticle ; and it is to the close adherence of this that 

 their lustre is sometimes due. The carbonaceous perithecia, 

 for the most part, burst irregularly ; and they are, in most 

 cases, easily distinguishable from Sphceria by their crust, which 

 is sometimes highly developed, and beautifully sculptured. 

 The species are probably numerous, but at present they have 

 not been sufficiently studied, and as the fronds vary greatly 

 under different circumstances no correct estimate can be made 

 of numbers, till the fructification has been extensively ex- 

 amined. The species are developed principally on the upper 

 surface of thick tropical leaves, which suffer greatly, and soon 

 lose all their beauty from their repeated attacks. It may be 

 dou.bted whether all the genera which are associated by 

 authors, are as nearly allied as they suppose. The analogy 

 between Strigula and Asterina is very close, and both con- 

 cur in choking up the pores of the leaves and preventing the 

 admission of light to the tissues. 



430. If the tribe be confined to Strigula and its allies, it 

 must be considered as essentially tropical, with a few outlying 

 species. In a few cases, where the patches are well defined, 

 and there is no admixture of other Cryptogams, the appear- 

 ance is neat and striking. Liraboria is the typical genus of 

 the tribe. I have had no opportunity of examining the struc- 



