APPENDIX. 393 



zoospores formed from cell-contents and breaking out from 

 the surface, or motionless spores from the whole contents 

 of a cell. 



1. Ulva. Frond plane, simple, or lobed, of double layer 

 of cells, closely packed, producing zoospores. U. lactuca. 

 (latissima) U. Linza. 



2. Enter omorphi. Frond hollow, simple, or branched, 

 of a single layer of cells, closely packed, forming a sac or 

 tube, with zoospores. E. intestinalis. 



3. Monostroma. Frond flat or saccate, simple or lacer- 

 ate-lobed, forming a single layer of cells, which are scat- 

 tered in a homogeneous membrane, with zoospores. M. 

 bullosum. 



4. Prasiola. Frond membranous, lacerate-lobed, of sin- 

 gle layer of cells in simple or compound lines, or groups 

 multiple of four ; spores from whole contents of cells, mo- 

 tionless. P. callophylla, crispa,furfuracea^ and stipitata. 



5. Schizogonium. Frond filiform, dilated here and there 

 into flat ribands, with two or four rows of cells ; spores 

 from whole contents, motionless. S. percursum. S. l&te- 

 vireus. S. murale. 



11. PALMELLACE^;. Plants forming gelatinous or pul- 

 verulent crusts on damp surfaces of stone, wood, etc. 

 Masses of gelatinous substance, or pseudo-membranous 

 expansions or fronds, of flat, globular, or tubular form, of 

 one or numerous cells, with green, red, or yellowish con- 

 tents ; spherical or elliptical form, the simplest being iso- 

 lated cells (in groups of two, four, eight, etc.) ; others 

 formed of some multiple of four, the highest of compact, 

 numerous, more or less closely conjoined cells. Reproduce 

 by cell-division, by conversion of cell-contents into zoo- 

 spores, and, by resting spores formed sometimes after 

 conjugation, in other cases probably after fecundation by 

 spermatozoids. 



