SOIL-WATER CULTURE TECHNIQUE 25 



Anthophysa, and other iron flagellates were grown. As a rule the 

 amount of dissolved organic matter has to be kept low. 



CHRYSOPHYTA (Bacillariophyceae): If the media are well 

 adapted multiplication is good. Small species of Navicula and 

 Nitzschia often overgrow other algae which have not been 

 sufficiently washed. 



CHRYSOPHYTA (Xanthophyceae) : Every species so far 

 tested could be grown, including, among others, Ophiocytium, 

 Botrydium and Tribonema. 



PYRRHOPHYTA (Peridinieae) : Only species of Peridinium 

 have been cultured. These multiply and keep exceedingly well. 



PYRRHOPHYTA (Cryptophyceae) : Almost every cell of the 

 dozens of forms tested multiplied well, whereas pure cultures 

 generally could not be obtained. Chilomonas and Cyathomonas 

 also grew well. 



CHLOROPHYTA (Volvocales) : In many instances soil ex- 

 tract is better than soil-water cultures, e.g., for the three British 

 species of Volvox. Only in soil-water cultures could be grown: 

 Chlamydobotrys and Mesostigma which both need an additional 

 organic ingredient. Attempts at purification in bacteria-free me- 

 dia failed. In acid peat with water but without soil Carteria acid- 

 icola John grows well. Addition of soil or soil extract prevents 

 growth, whereas ammonium-salts up to about 0.05 per cent pro- 

 long multiplication. An exceptional case is also the larger Chla- 

 mydomonas spharerella (nom. prov.) which is popular for demon- 

 stration. It grows well in good light with dilute mixtures of 

 acetate, beef extract, and peptone, but refuses to multiply in soil- 

 water cultures. Of colorless genera, Polytoma, Hycdogonium, 

 Polytomella thrive in soil-water cultures with starch or cereal 

 grains. 



CHLOROPHYTA (Zygnematales) : Media have to be well 

 chosen. Spirogyra, Mougeotia, Zygnema, Cosmarium and other 

 desmids from non-peaty habitats can be grown easily with small 

 amounts of soil. Hyalotheca and some others grow best in peat 

 with water, but experience with species from acid bogs is limited. 



