. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Theoriginal cap is therefore often left in a lateral position somedistance behind the growing apex, which develops a new .the growth of the branch proceeds a repetition of thislateral displacement of apical caps results in branches withseveral lateral excrescences (West & Hood, 11) ; fig. 202 C. In the division of the apical cell the transverse wall arisesas an annular ingrowth from the middle region of the lateralwalls. In some specie
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . Theoriginal cap is therefore often left in a lateral position somedistance behind the growing apex, which develops a new .the growth of the branch proceeds a repetition of thislateral displacement of apical caps results in branches withseveral lateral excrescences (West & Hood, 11) ; fig. 202 C. In the division of the apical cell the transverse wall arisesas an annular ingrowth from the middle region of the lateralwalls. In some species the transverse walls are larnellose likethe lateral walls. Wildeman (99) has shown that injuries to the thallus ofTrentepohlia and Phycopeltis result in rapid Fig. 200. Semi-diagram-matic figure of thestructure of the wall ofthe apical cell of (Beinsch)De Toni var. ceylanicaW. & G. S. West. Theinnermost layer of cellu-lose (I) is filled in cp., apical cap. (AfterWest & Hood.) There is normally one nucleus in each cell, but in old cells several nucleihave sometimes been detected. There are several disc-shaped or band-shapedchloroplasts in each cell, without pyrenoids. The green colour is in somespecies masked by hsematochrome, some species of all the genera having anorange or red colour. The large quantity of haematochrome probably acts asa screen to the chloroplast against too intense light. Trentepohlia cyaneaKarsten (91) is bluish in colour and Phycopeltis nigra Jennings (96) isblack, but in these and certain other forms the unusual colour is due to theimpregnation of the cell-walls with some dark pigment. Reproduction most commonly occurs by zoogonidia, which are liberatedfrom specially differentiated z
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