

1919] 



WEBB — SPORE GERMINATION AND H ION CONCENTRATION 



207 



Methods 



The methods employed in this investigation, as described by 

 Clark ('99) and Duggar ('01), are substantially those used by 

 others in this laboratory. 



Organisms. — The fungi used were Aspergillus niger } Penicillium 

 cyclopium, Fusarium sp., Botrytis cinerea, and Lenzites saepiaria. 

 An attempt was made to use Colletotrichum lindemuthianum, 

 but, owing to the failure to obtain germination in the control 

 culture solutions, this organism was discarded. In the test- 

 tube cultures from which the spores were obtained, the fungi 

 were grown on potato agar made according to Duggar, Severy, 

 and Schmitz ('17); i. e., 230 gms. of potato were cut into small 

 pieces, autoclaved in 1 litre of water for 1 hr. at 15 lbs. pressure, 

 filtered while hot, 15 gms. of agar added, the mixture then auto- 

 claved for 15 minutes at 15 lbs., correction made for loss of 

 water, and finally tubed, sterilized, and slanted. The cultures 

 were allowed to grow at room temperature, and the spores were 

 always taken from cultures that were from 10 to 15 days old. 



Culture solutions. — The composition of the culture solutions 

 was based primarily on Clark and Lubs's ('17) titration curve of 

 ortho-phosphoric acid. Stock solutions of M/5 mannite in 

 M/10 H3PO4 and M/5 mannite in N/5 NaOH were made. Into 

 sterile Pyrex flasks, 100 cc. of the M/5 mannite-M/10 H 3 P0 4 

 solution were placed, and increasing proportions of M/5 man- 

 nite-N/5 NaOH were added. The flasks were plugged with 

 cotton and sterilized at 15 lbs. pressure for 15 minutes, after 

 which the hydrogen ion concentrations were determined by the 

 colorimetric method as outlined by Clark and Lubs ('17). The 

 procedure was as follows: 



To a test-tube containing a 10-cc. portion of the culture fluid 

 the proper indicator was added, and the color developed com- 

 pared with the colors obtained upon the addition of the same 

 indicator to tubes containing equal quantities of standard buffer 

 solutions. All solutions were made from the best chemicals, 



purified according to Clark and Lubs ('17), and made up with 

 doubly distilled water. A series of solutions was thus obtained 

 ranging in hydrogen ion concentration from P H 2.8 to 10.0 + . 

 In nearly every case the determined value was identical with 





