3G4 IMPROVEMENT IN THE ARRANGEMENT OF FERNS. 



kingdoms or branches; and to obtain a truly natural classification of 

 plants, we must determine within each well marked assemblages, corres- 

 ponding with the position of classes, under which will stand the alliances 

 and orders or great families, so as to embrace the whole kingdom. At 

 present we will confine our attention to the sub-kingdom, Acotyledoneae, 

 and to its highest class, Acrogense, of which we have noted the common 

 characters. It manifestly contains three of those divisions which 

 Lindley denominates alliances, and as custom in Botany has otherwise 

 appropriated the term order, we can perhaps do no better than to adopt 

 his name. Here, then, beginning with the lowest structure, we have, 



1st. Equisetales, with sporangia dependent from the peltate scales of 

 little strobili : spores surrounded by a membrane splitting spirally 

 into two bands. Stems branched, articulated, with fimbriated 

 sheaths at the joints, and the branches whorled around them. 

 One order. Equisetacege. 



2nd. LycopodAales. Sporangia exannulate not dependent. 

 Orders : 



1. Marsileacege : sporangia radical multilocular. 



2. Lyeopodiaceas : sporangia axillary, bi or tri-valvate. 



3. Ophioglossaceae : sporangia bivalvate connate on the edge of 



the contracted fertile frond. Aestivation straight. 



3rd. Filtcales. Sporangia more or less annulate, aestivation circinate. 

 Orders : 



1. Osmundacege : sporangia with* the ring obsolete or imperfect. 



Tribes: 



1. Marattiinse : ring obsolete, sporangia more or less 



confluent. 



2. Schizaeinse : ring terminal, 



3. Osmundinse : ring imperfect. 



2. Cjatheacese : Sporangia with the ring oblique or eccentric. 



Tribes : 



1. Gleicheneinse : sporangia sessile ornearly so, bursting 



longitudinally. 



2. Hymenophyllinse : fronds cellulari-retieulate. 



3. Cyatheinse : sporangia pedicellute, bursting laterally. 



