76 BARRINGTON MOORE Vol. Ill, No. I 



Influence of Humus on Wheat. — The influence of humus on the rate of 

 growth of wheat was very marked, although the proportionate increase on 

 the humus was considerably less than in the case of the trees. Is this a 

 further indication that plants requiring fertile soil respond less readily to 

 humus than those which do well on poorer soil? 



The perio3~of growth was only 26 days, further growth on the humus 

 being hampered by the wire screens. This is, however, sufficient with such 

 a rapidly growing plant to show the influence of humus. At the end of the 

 26 days the plants on the sand were dying back at the tops (see fig. 5). The 

 green and dry weight per plant, exclusive of roots, are given in Table 3. 



Table 3. Green and dry weight of wheat tops on unlimed soils 



Green weight per plant. Dry weight per plant. 

 Soil grama grams 



Sand 073 .020 



Sand with humus 174 .048 



Humus 343 -0792 



The wheat plants on the humus showed the effects of the low carbohydrate 

 and high nitrogen content of the soil by forming several stems to the plant 

 instead of a single stem as with those on the sand. This agrees with the 

 results already obtained by several workers (7 and 8) on the influence of 

 the carbon-nitrogen ratio. 



Influence of Alkalinity 



Heavy Application of Burnt Lime. — The effect of alkalinity produced by 

 the moderately heavy applications of air-slaked burnt lime was very unfavor- 

 able to all species except cedar. It is significant that cedar came up and looked 

 thrifty on the limed mixture of sand and humus, whereas it died back on the 

 unlimed, and that growth on the limed pure sand was practically the same as 

 on unlimed sand instead of much inferior as it was with the other trees. On 

 the limed humus it was prevented from coming up by the crust until a four 

 days' rain from July 18 to 22 permitted the seeds to germinate on the surface, 

 after which they grew well. Thus the alkalinity, though perhaps not favor- 

 able to the cedar, was far less unfavorable than to the other trees. The be- 

 havior of cedar corroborates Femald's work on lithological factors (2), in 

 which he brings out the preference of the species for limestone soils. 



The unfavorable effect of alkalinity agrees with the work of Hoagland 

 (5), who found that for barley alkalinity is more unfavorable than acidity 

 for the same departure from the neutral point; here we see that alkalinity 

 is harmful to trees as well as to barley. It is even probable that, except for 

 certain trees like cedar, which grow best on lime soils, alkalinity is even more 

 injurious to trees than to most crop plants. 



The sugar maple seedlings, being transplanted only two days after the 



