. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . , and two. Fig. 214. A, Zygnema stellinum (Vauch.) Ag., x 430. E, Z. Vaucherii Ag. var. star/mile (Hass.)Kirchn., x 430. C, Z. ericetorum (Kiitz.) Hansg., x 415. D, Z. leiospermum De Bary, x , Z. insigne (Hass.) Kiitz., x 330. F, Z. Ralfnii (Hass.) De Bary, x 430. ap, aplanospore. chloroplasts (except in Zygnema ericetorum), the latter being axile in Zygnemaand Pyxispora but parietal in Pleurodiscus (fig. 216 D). Each chloroplast isfurni
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . , and two. Fig. 214. A, Zygnema stellinum (Vauch.) Ag., x 430. E, Z. Vaucherii Ag. var. star/mile (Hass.)Kirchn., x 430. C, Z. ericetorum (Kiitz.) Hansg., x 415. D, Z. leiospermum De Bary, x , Z. insigne (Hass.) Kiitz., x 330. F, Z. Ralfnii (Hass.) De Bary, x 430. ap, aplanospore. chloroplasts (except in Zygnema ericetorum), the latter being axile in Zygnemaand Pyxispora but parietal in Pleurodiscus (fig. 216 D). Each chloroplast isfurnished with a central pyrenoid. In Zygnema the two chloroplasts are generally star-shaped, havingnumerous radiating branched processes (fig. 216 E). Z. ericetorum is anotable exception in which there is but one deeply constricted chloroplast, 344 Conjugate often twisted at the middle, each half having a central pyrenoid (fig. 215 Dand E). Moreover, in this species the two halves of the chloroplast, althoughirregularly lobed, are not produced into slender branched processes. Multiplication by fragmentation of the vegetative filaments is very unusualin Zygnema.
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