ALG^E. 



555 



others. Particular kinds of mould sometimes grow on the mucous 

 membrane of birds. Some mycodermatous Fungi are connected with 

 certain cutaneous and other diseases in the human species. Thus, 

 cellular filaments called Porrigophytes are found in the crusts of 

 Porrigo favosa, Mentagraphytes hi those of Mentagra or Sycosis menti, 

 and Aphthaphytes in Aphthae. 



1127. Order 220. Algte, the Sea-weed Family. Cellular plants 

 found both in salt and in fresh water. Fronds composed of variously 

 formed, often elongated cells, which are either simple or branched fila- 

 ments, continuous or articulated, separate, or combined in different 

 ways (fig. 29) so as to constitute fronds of various kinds (fig. 788). 

 Growth takes place by the division of cells, or by cellular prolonga- 

 tions, in the form of lateral branches. Eeproductive organs consist of 

 spores, which are contained in mother-cells or perispores (gl, around, 



791 792 



and ffTroga, seed), or sporocarps (x.^o;, fruit). These are sometimes 

 congregated together in receptacles of different sorts (figs. 788 c c, 

 789). The spores occasionally divide into 3 or 4 cells, constituting 

 tetraspores (rt-r^s, four). In addition to spores or sporocarps (fig. 

 791 sp), there are sometimes round, or clavate, or filamentous cellular 

 bodies present, to which some give the name of antheridia (fig. 791 /). 

 In some of the simplest Algae, the whole plant is concerned in producing 



Figs. 788-792. Frond and organs of reproduction of Fucus serratus, to illustrate the natural 

 order Algse. 



Fig. 788. The entire plant much diminished in size. /, Frond composed of cells, so united as 

 to form a flat expansion, c c, Conceptacles at the extremities of the frond, containing the organs 

 of reproduction. 



Fig. 789. Extremity of the frond covered with conceptacles. 



Fig. 790. Vertical section of a conceptacle, c, with its inner surface covered with spores 

 (sporocarps), and paraphyses, or antheridia. t, The superficial cellular tissue of the frond, in 

 which the conceptacle is buried, o, Foramen by which the conceptacle opens externally. 



Fig. 791. Spore, ip, covered with its perispore or sporocarp, p. f. Filaments or paraphyses, 

 by some called antheridia. 



Fig. 792. Spore, *, separated and deprived of its perispore or outer covering. 



