APPENDIX A 



185 



U tubes, A and .4 ', filled with sulphuric acid, are used to purify the 

 air. B is a long, hard-glass tube enlarged at one end for sterile cot- 

 ton and stopper. A and B are for use in the aeration of the soil (if 

 liquid culture media are used, these may be omitted). Tubes Z), E, 

 and A serve for watering ; the sterile air is passed through A , and E 

 then carries the water in flask 2 over into culture vessel 1. 



The large opening, O, in flask 1 carries a cylinder constructed as 

 shown by Fig. 45. 



A wire net is fastened to the sides of C and passes down to the 

 soil in flask 1. An outer glass cylinder 4~5 cm. in diameter and 



FIG. 44. Complete apparatus for growing seedlings under sterile conditions. 



(After Fred) 



1, Woulff flask containing soil; 2, Erlenmeyer flask containing sterile distilled water 



15 cm. in length fits very loosely around (7, in order to allow space 

 for cotton between C and the cylinder. Within (.' there is an inner 

 tube, about 1|;~1^ cm. in diameter and 20 cm. long, which reaches to 

 the wire net (see Fig. 45). In the top of this tube there is a cot- 

 ton plug. Between these two tubes cotton packing and three glass 

 rods about 0.4 cm. in diameter and 15 cm. long are placed. The cotton 

 must be packed loosely, with one open space, as seen in Fig. 45, 1. 



If soil is to be used, cover the bottom of flask 1 (Fig. 44) with 

 gravel, and fill this vessel with soil. Raise the water content of the 

 soil to 15 or 20 per cent, according to the type of soil. Now join 

 flask 2, which has been previously filled with distilled water. Fasten 

 a screw clip between D and E, in order to prevent the water in 



