[ 6 59 I 
eonfeqaently the moft abftrufe parts of botany, mpy 
neverthelefs be jufhly efteemed, without any exag- 
geration, one of the moft complete works extant of 
the kind. 
Dr. Hill, in his Hiftory of Plants, has difpofed 
them into five genera, under the following names : 
1. JJfnea, comprehending the hairy tree -mofles; 
2. Platyjma , flat-branched tree-modes, the lungworts, 
and others j 3. Cladonia , containing the orchel and 
coralline-modes j 4. Pyxidium , the cup-modes ; f. 
P lac odium, the cruftaceous mofles. 
The plants of this extenfive genus are very dif- 
ferent in their form, manner of growing, and gene- 
ral appearance :• on which account thofe authors,, 
who preferve them under the fame name, faw the 
propriety and neceflity of arranging them into dif- 
ferent orders and fubdivifions, that the fpecies might 
be diftinguifhed with greater facility. Upon the fame 
principle Dr. Dillenius and Dr. Hill have formed 
them into feveral genera. 
So far as the parts of fructification are diftinguifh- 
able in thefe plants, they appear in different forms 
upon different fpecies : on fome, in the form of tu- 
bercles j. on others, in the form of little concave 
difhes, called f cut ell & ;■ on others, . of oblong flat 
ihields or pelts. All thefe are conceived by Micheli 
and Linnaeus to be receptacles of male flowers. The 
female flowers and feeds are fufpeCted by the fame 
authors to be difperfed in the form of farina or dull 
upon the fame plants, and in fome inftances on fe- 
parate ones. Dillenius has not dared to determine 
any thing pofitively with regard to the real parts of 
fructification in thefe lichens : time will hereafter, it 
is to be hoped, throw more light upon the fubjeCt. 
4 P 2 In; 
