ON GENERA AND SPECIES. 21 
Hemionitis, Polypodium, Asplenium, Pteris, Blechnum, Lon- 
chites, and Trichomanes. The data upon which they were 
founded were derived, as in flowering plants, from the 
different modifications and position observed in their so- 
called organs of fructification. The chief difference con- 
sisted in the fructification—spore cases or sporangia—being 
produced either in defined round masses, or in lines, or 
densely crowded together on the under side of the frond, 
or in simple spikes or panicles formed by the whole or a 
portion only of the fertile frond being contracted. Thus, 
according to Linneus’ characters, all Ferns having their 
fructification in simple or racemose spikes belong to 
Osmunda and Onoclea ; in crowded masses to Acrostichum ; 
. in round masses or spots to Polypodium; in lines across 
. one another to Hemionitis; in lines diverging from the 
` mid-rib to Asplenium; in a line on each side of the mid-rib 
— to Blechnum; in a line or dots on the margin to Pteris and ` 
-~ -Adiantum; in a sinus on the margin to Lonchites ; and 
. inserted on the margin to Trichomanes. 
~ These Linnean genera are each composed of a greater : 
ad lesser number of species, each of which is presumed to 
. agree in the form and position of the fructification with the 
. respective generic characters as above stated. But the 
. more careful examination by later observers of the same 
=~ generic forms has revealed additional variations, which 
will come under notice as we proceed. It is worthy of 
remark, however, that the whole of the species of Ferns 
now known are capable of being referred to Linnean 
genera; but if such were done, species possessing Very - 
different appearances as regards habit and mode of growth 
unwieldly dimensions. E 
The first author of phan: after Linnæus was Dr. Sa 
would be brought together, and the genera age bao S 
