CRYPTOGAMS 



339 



are unknown in the latter group. According to the observations of PHILIPPS, 

 which, however, require confirmation, some of the Cyanophyceae which exhibit 

 movements possess cilia. 



The simplest Cyanophyceae consist of spherical cells ; this is the case with 

 species of Ckroococcus. In Gloeocapsa (Fig. 261), found on damp rocks and Malls, 

 the cells remain connected together after division into a gelatinous mass, forming 

 a multicellular colony. 



The species of Oscillaria, which occur everywhere in water or on damp soil, 

 are the simplest of the filamentous forms. The filament, which is usually provided 

 with a thick sheath, consists of similar flattened cells (Fig. 262). It can separate 

 into pieces. (hormogonia), which become free owing to the pressure of the sheath, 

 and grow into new filaments. In other filamentous Cyanophyceae specially modified 

 cells with their contents degenerated occur in the filament. The significance of 

 these heterocysts is not yet clear. The species of Nostoc (Fig. 263), whose bead- 

 like filaments are united by the swell- 

 ing of the cell-walls into more or less 

 spherical gelatinous colonies living on 

 damp soil or in water, afford an example 

 of this. 



ilany Cyanophyceae take part with 

 the Fungi in the formation of Lichens. 

 Some species also are endophytic and 

 inhabit cavities in other plants, e.y. 

 Anabaena in Azolla, Nostoc in some 

 Liverworts, in Lemna, and in the roots 

 of Cycas and Gunnera. 



CLASS III 

 Flagellata (Flagellates) 



The Flagellata are a group of uni- 

 cellular, aquatic organisms exhibiting 

 a wide range of form ; they combine 

 animal and vegetable characteristics, 

 and may be regarded as the starting- 

 point on the one side of unicellular 

 Thallophytes, on the other of the 

 Protozoa. 



The protoplast exhibits contractile 

 or amceboid movements, and is limited 

 by a denser protoplasmic layer and 

 not by a definite cell wall. One or 

 more cilia (flagella) are present as 

 motile organs. The protoplast con- 



Fio. 204. Eaylena gracilis. A, Form with green 

 chromatophores (ch) ; n, nucleus ; v, vacuolenml 

 red eye-spot ; g, flagellum. B, Hemisaprophytic 

 form with small green chromatophores. C, 

 Colourless saprophytie form occurring in nutrient 

 solution in absence of light. D, Resting cyst of 

 the form C ; r, red eye-spot. E, Germination of 

 the resting cyst of the form A by division into 

 four daughter cells which later escape. (After 

 /UMSTEIN ; A,C, x630; B, X650; D, E, xlOOO.) 



tains a nucleus, a pulsating vacuole, 

 and in many species well -formed green, yellow, or brownish -yellow chromato- 

 phores. Other forms are colourless and live saprophytically ; many are also able 

 to take up solid particles as food. 



