SPERMATOPHYTA 69 



sion of labor continue until a highly differentiated sporophyte results, 

 the mature "fern plant." 



Class i . Filicine^ or True Ferns (Homosporous) 



Family PolypodiacejE. — Sporangia with annulus vertical and 

 incomplete. 



The rhizomes of Dryopteris filix-mas and Dryopteris marginalis 

 are official in the U. S. P. The fibrovascular bundles of these are con- 

 centric in type but differ from the concentric f .v. bundles of some mono- 

 cotyledons in that xylem is innermost and phloem surrounds the 

 xylem. 



Class 2. HYDROPTERiDiNEiE, OR Water Ferns (Heterosporous) 



Family Salviniace^, floating ferns with broad floating leaves and 

 submerged dissected leaves which bear sporocarps. Ex. : Salvinia and 

 AzoUa. 



DIVISION IV.— SPERMATOPHYTA (PHAl^TEROGAMIA) 



Plants producing real flowers and seeds. The highest evolved 

 division of the vegetable kingdom. 



SUBDIVISION I.— ANGIOSPERMIA OR ANGIOSPERMS 



(Plants with covered seeds) 



Class A. — Monocotyledons 



A class of Angiospermia characterized by the following pecul- 

 iarities : 



One cotyledon or seed leaf in the embryo. 



Stems endogenous with closed collateral or concentric fibrovascular 

 bundles, which are scattered. 



Leaves generally parallel veined. 



Flowers trimerous (having the parts of each whorl in 3's or multiple 

 thereof). 



Secondary growth in roots generally absent. 



Medullary rays generally absent. 



