ALG. 755 
Sub-order 3. Chlorosporex, Chlorospermex, Confervoidex, or 
Green-coloured Alge.—Unicellular or multicellular Algze, 
growing in fresh or salt water, or in moist situations ; 
usually of a bright green colour, or rarely red. Illustrative 
Genera :—Conferva, Plin. : Palmella, Agh. ; Spirogyra, Link. 
Sub-order 4. Diatomacex.—The following diagnosis is modified 
from Henfrey:—Microscopic unicellular plants, occurring 
isolate or in groups of definite form, usually surrounded by a 
Hreewl25, 
Fig. 1125. A species of Diatomaceous Alga (Diatoma marinum) divided 
into parts by mevismatic or fissiparous cell-division. The parts are 
seen to be striated. 
gelatinous investment, the cells exhibiting more or less regular 
geometrical outlines and enclosed by a ~ membrane, striated 
(fig. 1125) or granular, either simply tough and continuous 
( fig. 1126), or impregnated with silex and separable into 
valves (fig. 1125). Reproduction by spores formed after 
conjugation of the cells which have previously lost or thrown 
off their cellulose walls (fig. 1126), or by division (jig. 1125). 
The Diatomacex are again divided into two sections or tribes. 
1. Diatomee (fig. 1125). Natives of fresh, brackish, or salt 
water, or of moist ground, of a brownish or olive colour, 
Fie. 1126. 
Fig. 1126. Two Desmidiaceous Algz (Docidium Ehrenbergii) after conjuga- 
tion, with a 7esting or inactive spore between them, (After Ralfs.) 
valvular, and invested by a siliceous membrane. TIlustrative 
Genera -—Diatoma, DC.; Navicula, Bory. 2. Desmidiex 
(fig. 1126). Found only in fresh water, of a green colour, 
continuous, containing starch, and not invested by a siliceous 
membrane. Illustrative Genera :—Closterium, Nitzsch ; Des- 
midium, A gh. 
