62 



THE ALGAE 



akinetes. They are golden green in colour and both species frequent 

 brackish ditches. Some authorities retain this genus in the Ulva- 

 ceae but the differences would appear to be sufficiently distinct to 

 justify its removal to a separate family. 



Sphaeropleaceae : Sphaeroplea {sphaero, sphere; /j/^a, full). Figs. 



33.34 

 This genus is widely distributed but is only frequent locally, 

 being most abundant on ground that is periodically flooded by 

 fresh water. The long, free, unbranched filaments consist of 

 elongated coenocytic cells containing up to seventy annular parietal 

 chloroplasts with pyrenoids. The plastids have denticulate margins 

 and occupy the periphery of discs of cytoplasm, the discs being 



1 



Fig- 33 Sphaeroplea. A, S. annulina, portion of thallus. B, 5. 

 annulina chloroplast. C, structure of septum in 5. africana 

 ( X 375). D, female plant with ova and antherozoids. E, male plant. 

 F, young zygote. G, zygote with thickened wall. H, I, young 

 gametophytes. J, spores emerging from zygote. K, L, 5". africana, 

 transverse sections across the septa ( x 375). (A-C, K, L, after 

 Fritschi D-J, after Oltmarms.) 



