[Vor. 8 
290 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
CULTURE SOLUTIONS 
Mannile.—The titration curves of the various liquid media 
employed in this study are shown in fig. 1. The composition 
of the single nutrient or mannite culture solutions was based 
primarily upon the Clark and Lubs (717) titration curve of ortho- 
phosphoric acid, and the methods of procedure are the same as 
those previously described by the writer ('19). Stock solutions 
of M/5 mannite in M/10 H,PO, and M/5 mannite in N/5 NaOH 
were made. Equal quantities of the M/5 mannite-M/10 H,PO, 
solution were placed in each Pyrex flask, and successively in- 
creasing proportions of M/5 mannite-N/5 NaOH were added. 
The flasks were plugged with cotton, sterilized at 15 pounds 
pressure for 15 minutes, and allowed to stand at least 24 hours 
before making H-ion determinations. Perfect agreement be- 
tween calculated and determined values always resulted except 
within the range Py 8.0-10.0 where a shift towards neutrality 
frequently occurred. Such deviations, however, might well be 
attributed to the extreme lack of buffer action within this range, 
as shown by fig. 1, and also to any hydrolysis of mannite that 
might occur during sterilization. A relatively small precipitate 
invariably occurred in the extreme alkaline cultures. 
Czapek's solution.—Czapek's full nutrient solution was made 
according to the formula published in a recent paper by Zeller, 
Schmitz, and Duggar (719): MgSO, 7H,O, 0.5 gm.; KH,PO,, 
1.0 gm.; KCl, 0.5 gm.; NaNO,, 2.0 gms.; FeSO,, 0.01 gm.; cane 
sugar, 30.0 gms.; H,O, 1000 cc. The original nutrient solution 
was prepared by adding 600 cc., instead of 1000 cc., of distilled 
water. This method, which has been described by Karrer and 
Webb ('20), and which will be restated briefly, allows dilutions 
of the various solutions by the addition of regulated amounts 
of acid or alkali and water for the adjustment of various H-ion 
concentrations without materially affecting the concentrations 
of the nutrient salts or constituents. The acid and alkali used 
with this particular medium were N/5 HCl and N/20 KOH. 
This strength of alkali is more satisfactory than one more con- 
centrated, the latter introducing difficulties in securing those 
reactions less acid than Py 4.5-5.2—the H-ion concentration 
