72 STRUCTURAL AND PHYSIOLOGICAL BOTANY. 



podetium, having shields on the margin 338 . Soredia, or powdery masses 3 ^ ; 

 they are also called globuli and glomtruli. Lacuna, are pits of the thallus . 

 Excipulm is that part of the thallus which forms the rim and base of shields. 

 Tftallodes signifies formed of the thallus. 



607. ALGACEJS are submersed plants, equally destitute of any 

 kind of tissue, except the cellular, and propagated by spores 

 (590) lodged in various parts of the system. 



608. The sporules either lie freely in the whole substance of 

 such plants, or are collected in particular cells 3 ", or occupy 

 jointed filaments 324 , or are placed in spheres 321 , occupying the 

 circumferences of expansions of the thallus (605). 



609. There are also other modes of multiplication. 



Among the special terms employed by writers on this order, the following may 

 be enumerated as the principal. Among their reproductive organs are gongyli, 

 or hard round deciduous bodies ; granula, or large spores ; sporidia, or bodies 

 resembling spores, but not such ; sporangia or coniocysta, or spore-cases 321 325 . 

 Hypha is a filamentous thallus ; phycomatcr is the gelatine in which the 

 spores of some begin to vegetate ; peridiolum is a membrane immediately 

 covering the spores ; vesicula are air-bladders that enable some species to 

 float. 



610. FUNGACE.E, which are the lowest form of vegetation, 

 are also cellular, some of their cells however containing 

 spiral threads, and are propagated by spores. 



611. In the highest forms, two kinds of organs are de- 

 tected : one, cystidia 545 , are conical naked elevations ; the 

 other, basidia 3 * 5 , are also conical elevations, but they bear 

 spores in definite number on their apex. 



