54 CONFERVOIDE.E. 



1, 2, or 4 cilia), akinetes or aplanospores ; the last named may 

 germinate immediately, or only after a period of rest. Sexual re- 

 production takes place by the conjugation of gametes of about the 

 same size, each having two cilia (Fig. 52 d). The zygote of 

 Ulothrix, on germination, produces a brood of zoospores which 

 swarm for a time and then elongate to become 7/o^/m',-filaments 

 (alternation of generations). The gametes may also germinate 

 without conjugation in the same manner as the zoospores. The 

 principal genera are : Ulothrix, Hormidium, Conferva, Micro- 

 spora. Ulothrix zonata is very common in running fresh water. 

 Nearly all the species of Hormidium occur on damp soil, tree- 

 stems and stones. 



Order 3. Chaetophoraceae. The thallus consists of a single, 

 branched, erect or creeping filament of cells, often surrounded by 

 mucilage. The cells have only one nucleus. Asexual reproduc- 

 tion by zoospores with 2 or 4 cilia, by akinetes, or aplanospores. 

 In many, conjugation between gametes with 2 cilia may be found. 

 They approach on one side, Ulothricaceae, and on the other, My- 

 coideacea?. The principal genera are : Siigeoclonium, Draparnahlia, 

 Cluvtophora, Enloderma, Aphanochtvte, Herposteiron, Phceuthamnion, 

 Cltlorotylium, Trichophihis, Gongrosira, TrentepohJia. Most of the 

 species of Trentepoklia are coloured red by the presence of a red 

 colouring material, which occurs in addition to the chlorophyll. 

 They are aerial Algae which live on stones (T. julithus, "violet 

 stone," so named on account of its violet-like odour in rainy 

 weather), on bark and old wood (T. umbrina'), or on damp rocks 

 (T. aurea). Trichophilus icelckeri lives in the hair of Bradypus. 



Order 4. Mycoideaceae. The thallus is discoid, consisting of one or more 

 cell-layers, and is always attached. Asexual reproduction by zoospores with 2 

 or 4 cilia. Sexual reproduction in some species by the conjugation of gametes 

 with 2 cilia. This order forms the connecting link betweeu Cluctop]ior(tct<c 

 and Coleochcetacea. The species occur in fresh water (Cluetopeltis) as well as 

 iu salt (Pringtsheimia), on the carapace of tortoises (DermatOphyton = Epiclem- 

 mydia), or endophytic between the cuticle and the epidermal cells of the 

 leaves of tropical plants, destroying the leaf-tissue (Mycoidea). 



Order 5. Cylindrocapsaceae. The thallus consists of a 

 simple (rarely, in parts, formed of many rows) unbranched 

 filament, attached in the young condition, which has short cells 

 with a single nucleus, and is enveloped in a thick envelope with 

 a laminated structure. Asexual reproduction by zoospores with 

 2 cilia, which are formed 1, 2, or 4 in each vegetative cell. The 



