SOIL ALGAE 217 



the development of various blue-green algae; dry soil will give the 

 spore-forming Nostococaceae, such as Anabaena and Cylindrospermum. 2 

 When a large quantity of soil is placed in tap water, various small 

 diatoms will always develop. When proteins are added to the soil and 

 covered with water, various Volvocineae, such as Chlamydomonas, 

 Karteria, Chlorogonium, Spondylomorum are obtained. 3 For the pur- 

 pose of isolating the algae, Robbins 4 used 500 cc. Florence flasks filled, 

 to their greatest diameter, with ground quartz, previously washed free 

 from all suspended matter. The flasks are plugged with cotton and 

 sterilized at 120°C. for 30 minutes. The soil is then shaken, for 5 

 minutes, with sterile water; an amount (25 cc.) equivalent to 10 grams 

 of soil is evenly distributed, with a sterile pipette, over the ground quartz 

 surface. The flasks are tipped to one side so as to offer both a moist 

 sand and a free water surface for the algae to grow on. The flasks are 

 kept in the greenhouse in a sunny place, then in a shady place. After 

 growth of algae has taken place, they are transferred to 1 per cent agar 

 medium with soil extract as a base. Some of the algal material is 

 shaken up in a test tube with a few cubic centimeters of sterile water, 

 then transfers are made, with a platinum loop, to tubes of liquefied 

 agar cooled to 42°C. The tubes are shaken and the agar is poured into 

 sterile Petri dishes. Growth of algae will appear in 2 or 3 weeks. The 

 cultures may then be transferred to insure purity. 



Moore and Karrer 5 placed about l\ inches of sand in pint milk bottles, 

 to which 150 cc. of a culture solution had been added. The bottles 

 were plugged with cotton and sterilized at 8 to 10 pounds pressure 

 for one-half hour. Because of the soluble material present in the sand, 

 the culture solution was one-half the strength of a modified Beijerinck 

 solution used by Moore. 6 



2 Beijerinck, M. W. t)ber oligonitrophile Mikroben. Centrbl. Bakt. II, 7: 

 561-582. 1901. 



3 Jacobsen, H. C. Kulturversuche mit einigen niederen Volvocaceen. Ztschr. 

 Bot. 2: 145-188. 1910. 



4 Robbins, W. W. Algae in some Colorado soils. Colorado Agr. Exp. Sta. 

 Bui. 184. 1912. 



5 Moore, G. T., and Karrer, J. L. A subterranean algal flora. Ann. Mo. Bot. 

 Gard. 6: 281-307. 1919. 



6 Moore, G. T. Methods for growing pure cultures of algae. Jour. Appl. 

 Microsc. 6: 2309-2314. 1903. 



