182 



PHYLUM TRACHEOPHYTA: 



Figure 11.18 Water fern types: 1, Marsilea; 2, Pilularia; and 3, Regnellidium. About natural size. 

 (Used by permission, from Morpfio/ogy of Vascular Plants; Lower Groups, Psitophytates to Filicates 

 by Artfiur J. Eames. Copyrigfit 1936. N. Y.: McGraw-Hill Bool< Co.) 



by a hair-like, bladeless leaf; about 40 species of Mar- 

 silea, mostly in tropical Africa and Australia, but in 

 most warm parts of the world (United States forms 

 are called either water clovers or pepperworts); water 

 ferns typically are found creeping upon the substrate 

 at the margins of bodies of water, but also are found 

 in wet mud and upon moist substrates; plants are 

 erect but leaves sometimes float in water. 



ORDER SALVINIALES (Floafing and Mosquifo Ferns) 



Diagnosis: fossil record obscure; like the Mar- 

 sileales are no more than an unfernlike family of the 

 Filicales; both are separated only for emphasis; plant 

 either a floating rhizome with whorls of two floating, 

 inflated leaves and one underwater dissected leaf, or 

 a rooted branched rhizome with moss-like leaves; 

 sporangia in modified structures (sporocarps) that 

 are associated with the leaves; two spore types pro- 

 ducing much reduced male and female gametophytes 

 (Figure 11.19). 



Occurrence: two genera of mostly perennial herbs 

 (one species of each genus is an annual) in a single 

 family, Salviniaceae; all are floating aquatics of warm 

 temperate and tropical regions but none are in Eu- 

 rope; about 10 species oi Salvinia (floating ferns), 1 in 

 the United States, and 6 species of Azala (mosquito 

 ferns), 1 in the United States. 



SPERM ATOPHYTES (Seed Plants): 

 Gymnosperms and Angiosperms 



Diagnosis: plants that produce true seeds; the 

 leaves are often large, relatively complex and 

 branched-veined (megaphylls), the stems and roots 

 are usually well developed; the veins are complex; 

 branching is mostly from a straight main stem but 

 often is modified into an irregular type; sporangia 

 producing two kinds of spores; differ from other two- 

 spore-type plants by greater reduction in the male 

 and female gametophytes and by some features in the 

 sporophyte embryo; smaller spores develop into dis- 



