28 FERNS OF KENTUCKY. 
that a separate classification is necessary. (Fig. 5.) See 
Plate L¥IX. 
The sUB-ORDER POLYPODIACEZ embraces what are gen- 
erally termed the true ferns, and is by far the largest group, 
not only of ferns indigenous to the United States, but of 
all existing species. The arrangement of the fruit-dots is 
so varied in the genera of this family that Prof. Eaton has 
separated it into five tribes: 
1. POLYPODIEA. 4. ASPIDIEZ. 
2. PTERIDEZ. 5. DAVALLIEZ. 
3. ASPLENIEZ. 
The following table, with references to the plates, will 
enable the student to understand more clearly the relation- 
ship of the genera to the tribes to which they belong: 
TRIBE 1. PoLypopIE#. Fructification on the back of 
the frond; no indusium; stipes articulated to the root-stock. 
PotyvpopiumM, .« .°...°. ‘Plates Tifand Ay. 
TRIBE 2. PTERIDE#. Fructification marginal or inter- 
marginal; provided with a general indusium; stipes not 
articulated; veins free in our species. 
ADIANTUM, 00 >. os 6 ce Pie ee 
PPERIS, i a et Se eee 
CHEILANTHES,.. 25-2) 4. 2.3) SPE 
PETETA, |... a sl ee ee ee eee 
ALLOSORUS. 
TRIBE 3. ASPLENIE&. Fructification elongated, cov- 
ered by a special indusium which is attached by one side 
to the fertile vein; stipes not articulated. 
WoopwaRDIA. 
ASPLENIUM, 60 05° >. “Sa Bite ae 
SCOLOPENDRIUM. 
-CAMPTOSORUS, *.0 sa) 2 >. 1) Plate Say 
