. The algae. Algae. 26o THE ALGAE analogues which, so far as general morphology is concerned, bear so much resemblance to chlorophycean groups that these forms are classed as Hetero- chloridales, Heterococcales, Hetero- siphonales and Heterotrichales. Heterochloridaceae : Chloramoeba (chlor, green; amoeba, changing). Fig. 147 This is a naked unicell which is analogous to certain members of the Volvocales, Dunaliella. The cells multiply by longitudinal division, but under adverse conditions eUipsoidal cysts with large oil globules are de- veloped and these form a resting Fig. 147 A
. The algae. Algae. 26o THE ALGAE analogues which, so far as general morphology is concerned, bear so much resemblance to chlorophycean groups that these forms are classed as Hetero- chloridales, Heterococcales, Hetero- siphonales and Heterotrichales. Heterochloridaceae : Chloramoeba (chlor, green; amoeba, changing). Fig. 147 This is a naked unicell which is analogous to certain members of the Volvocales, Dunaliella. The cells multiply by longitudinal division, but under adverse conditions eUipsoidal cysts with large oil globules are de- veloped and these form a resting Fig. 147 A, Chloramoeba heteromorphai cyst. B, the same, motile phase, c = chloro- plast, n= nucleus, z;= vac- uole. Cj flagellum structure in Monocilia. (After Fritsch.) Heterocapsaceae: Botryococcus (botryo, cluster; coccus, berry). Fig. 148 This fresh-water genus represents one of the palmelloid ana- logues of the Chlorophyceae, the principal species, B. braunii, forming an oily scum on ponds and lakes in spring and autumn, whilst in late simimer the cells are often coloured red by haemato- chrome. The colonies vary greatly in shape, the cells being radially arranged into spherical aggregates that are connected in a reticular fashion by tough, hyahne or orange-coloured strands belonging to the lamellated mucous envelope. The thin cell wall is said to con- sist of two unequal pieces, but despite this xanthophycean feature the alga is anomalous in that starch is said to be formed. The indi- vidual cells are surrounded by a thin membrane that becomes evident when they are squeezed out of their envelopes as some- times happens. Each cell is enclosed in a fimnel-shaped mucilage cup composed of several layers and prolonged at the base into a thick stalk. In old colonies the mucilage envelope swells up so that the cup structure is obscured, but although the sheath is so pre- dominant nevertheless its origin is not clearly known. The cells multiply by longitudinal division, whilst asexual rep
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Keywords: ., bo, bookcentury1900, bookcollectionbiodiversity, booksubjectalgae
