Fig, 154 Vaucheria. A, V. sessilis, germinating zoospore. B, V. 

 piloboloides, developing aplanospore. C, V. piloboloides, escape of 

 aplanospore. D, V. geminata, thread with cysts. E, escape of 

 amoeboid protoplast from cyst. F-I, V. repens, development and 

 escape of compound zoospore. J, regeneration and formation of 

 septa in injured thalli. K, sex organs of V. sessilis ( x 100). L, sex 

 organs of V. terrestris ( x 100) .M, sex organs of V. geminata ( x 100). 

 N, V. geminata, germinating aplanospore. O, germinating zygote. 

 Pj zygote with four haploid nuclei. Q, portion of compound zoo- 

 spore, much magnified. (A, D, E, N, O, after Oltmanns; B, C, F-J, 

 Q, after Fritsch; K-M, after Hoppaugh; P, after Hanatschek.) 



native or mercerized cellulose as in other members of the Chloro- 

 phyceae, whilst the discoid chloroplasts, which lack pyrenoids, 

 contain more than the normal amount of carotinoid pigments. Oil 

 forms the principal food reserve, except that under constant illumi- 

 nation starch may be formed. It is in these biochemical characters 

 that Vaucheria indicates its relationship with other members of the 

 Xanthophyceae. So far as reproduction is concerned it presents 

 anomalies whether placed in the Siphonales or Heterosiphonales. 

 Although most workers now place the genus in the Xanthophyceae, 

 there are a few who still feel that the evidence is not yet quite 

 sufficient. 



The plant consists of a colourless basal rhizoidal portion from 

 which arise green, erect aerial filaments with apical growth and 

 monopodial branching. Septa are only formed in connexion with 



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