2. CHLORELLA Beij. Occurring frequently on damp ground, bark of trees, etc., dividing into numerous daughter-cells, probably reduced zoogonidia (Fig. 23). Chodat distinguishes between _Cystococcus_ and _Chlorella_ in that _Cystococcus_ may form zoospores (though rarely), _Chlorella_ only aplanospores. He found three gonidial species, _Chlorella lichina_ in _Cladonia rangiferina, Ch. viscosa_ and _Ch. Cladoniae_ in other _Cladonia_ spp. 3. COCCOBOTRYS Chod. The cells of this new algal genus are smaller than those of _Cystococcus_ or _Protococcus_ and have no pyrenoid. They were isolated by Chodat from the thallus of _Verrucaria nigrescens_ (Fig. 24), and, as they have thick membranes, they adhere in a continuous layer or thallus. Chodat also claims to have isolated a species of _Coccobotrys_ from _Dermatocarpon miniatum_, a foliose Pyrenolichen. 4. COCCOMYXA Schmidle. Cells ellipsoid, also without a pyrenoid. Two species were obtained by Chodat from the thallus of _Solorinae_ and are recorded as _Coccomyxa Solorinae croceae_ and _C. Solorinae saccatae_. _Coccomyxa subellipsoidea_ is given[284] as the gonidium of the primitive lichen _Botrydina vulgaris_ (Fig. 25). The cells are surrounded by a common gelatinous sheath. [Illustration: Fig. 24. _Coccobotrys Verrucariae_ Chod. from culture × 800 (after Chodat).] [Illustration: Fig. 25. _Coccomyxa subellipsoidea_ Acton. Actively dividing cells, the dark portions indicating the chloroplasts × 1000 (after Acton).] 5. DIPLOSPHAERA Bial.[285] _D. Chodati_ was taken from the thallus of _Lecanora tartarea_ and successfully cultivated. It resembles _Protococcus_, but has smaller cells and grows more rapidly; it is evidently closely allied to that genus, if not merely a form of it. 6. UROCOCCUS Kütz. Cells more or less globose, rather large, and coloured with a red-brown pigment, with the cell-wall thick and lamellate, forming elongate strands of cells (Fig. 26). Recorded by Hue[286] in the cephalodium of _Lepolichen coccophorus_, a Chilian lichen. Fam. TETRASPORACEAE. Cells in groups of 2 or 4 surrounded by a gelatinous sheath. 1. PALMELLA Lyngb. Cells globose, oblong or ellipsoid, grouped without order in a formless mucilage (Fig. 27). Among lichens associated with _Palmella_ are the Epigloeaceae and Chrysothricaceae. [Illustration: Fig. 26. _Urococcus_ sp. Group of cells much magnified (after Hassall).] [Illustration: Fig. 27. _Palmella_ sp. × 400 (after Comère).] [Illustration: Fig. 28. _Gloeocystis_ sp. × 400 (after Comère).] 2. GLOEOCYSTIS Naeg. Cells oblong or globose with a lamellate sheath forming small colonies; colour, red-brown (Fig. 28). This alga along with _Urococcus_ was found by Hue in the cephalodia of _Lepolichen coccophora_, but whereas _Gloeocystis_ frequently occupies the cephalodium alone, _Urococcus_ is always accompanied by _Scytonema_, the normal gonidium of the cephalodium.