.. Rerns at their respective periods. 
on o GENERA AND SPECIES. 
sporangia, to which the term paraphysis is given. In 
 Amphidesmium, Lophosoria, Trichopteris, and several species EL 
of Alsophila, numerous simple or articulate hairs are mixed - 
` with the sporangia, which —— to the sori a woolly or 
hirsute appearance. 
The above is a general view of the form and position of 
the different organisation of Ferns, and furnishes data for 
the definition of genera and their arrangement; but as in 
many instances of botanical definitions, there are always 
exceptions to normal forms and position of parts, even to 
the sori being produced on the under side of the frond, as 
in Polystichum anomalum, a native of Ceylon; in some of 
its fronds the sori are as abundantly produced on the upper 
side as on the under, and bear the characteristic peltate 
indusium. The same also occurs in Trichiocarpe Moorei, a 
native of New Caledonia. Such seems to be the normal 
state of these two species even in native specimens, as 
also in plants cultivated in Kew. 
Ke THE GENERA OF EARLY AUTHORS AND THEIR SYSTEMS 
SCH OF CLASSIFICATION. 
Hens described the principal organs of Ferns, by means. 
of which genera are defined and classified, I now proceed. 
_to give a brief review of the progress of Pteridology from 
_ the time of Linnens to the present, noting the works ¢ 
_ the principal systematic authors who have from time ! t 
| time collated and characterised the genera and pue ) 
It appears that only about one hundred SS " 
|species were known to Linneus. These he classified 
[under eleven genera—viz. : : Osmunda, = Acrostich u 
