Ash content was determined as follows: At least 1 g of dry stems, ground to 60 mesh, was ashed in a muffle furnace at 650°C for 18-24 h. Ash content was calculated by weight difference. Carbohydrate and lig­nin compositions of untreated and treated straw samples were deter­mined by quantitative saccharification using the method of Saeman et al.

(11) . Two aliquots of each sample were analyzed by quantitative saccha­rification for each of the three replicate columns at each condition, for a total of 12 independent measurements of each composition. Carbohy­drate analyses were done by high-performance liquid chromatography using a Bio-Rad HPX-87P carbohydrate column as previously described

(12) . The acid-insoluble fraction from the quantitative saccharification was ashed at 650°C, and Klason lignin with extractives was calculated by weight difference. The amounts of glucan and xylan degraded per 100 g of initial weight were calculated by mass balance assuming that the sum of lignin, ash, and extractives remained constant. The percentage conver­sions of glucan and xylan (AG and AX, respectively) were then calculated by dividing by the initial basis weight of each and multiplying by 100.