Fig. 18: 1 and 2, Thelypteris normalis: 1, frond and rhizome, x %; 2, segments 

 with sori, x 3. 3, Thelypteris dentata: 3, segments with sori, x 3. 4, Thelypteris Tor- 

 resiana: 4, pinna (x %) and segments with sori, x 3. (From Correll in Lundell's Flora 

 of Texas, Vol. 1, PI. 34). 



