1. Shade decreases evaporation and transpiration and thereby increases the soil-moisture content of the superficial soil layers. This increase in soil moisture content is best shown by the accompanying diagram. This conclusion agress with the results obtained by Stewart and Hasselbring who grew tobacco in shade tents. 2. Shade accelaerates germination, that is seeds germinate sooner in the shade than in the light. This acceleration is due to the increase in soil-moisture content spoken about above. Burns reached the conclusion that shade reduces the temperature of the soil and delays germination. Evidently there is a delicate balance between soil moisture and soil temperature, so that a slight deficiency in either might delay the germination process. In Burns's case the temperature of the soil was so low, that in spite of the fact that there was sufficient soil moisture, germination was delayed. In the present investigations soil temperature was kept at an optimum and measured differences in soil moisture were sufficient to result in an acceleration of germination in the shade cultures. One unfortunate fact about Burns's work was that he failed to take into account soil moisture. In his experiments it must be assumed that there was sufficient soil moisture for germination. But there is nothing in his report which does not indicate that there was too much soil moisture. The reciprocal relation between soil temperature and soil moisture is well known. Furthermore there is an intimate relation between soil moisture and soil aeration and germination. Such factors as these were evidently not taken into account to explain the delay in germination in the experiments cited. 3. Shade increases the length of the germination period. This bears out to a certain extent Pittauer's experiments which showed that germination proceeds more rapidly in the light than in the shade. 4. The germination curve of seeds sown in the shade rises more rapidly than the curve of seeds sown in the light. This conclusion does not agree with the results obtained by Pittauer. 5. The final germination per cent. is usually higher in the case of seeds sown in the shade than those sown in the light. This conclusion, based upon abundant evidence, is not in accord with some work done by Atterberg which showed a greater germination per cent. in the presence of light than in the absence of it. 6. Light plays absolutely no part in the germination of tree seeds; in fact shade has been found to be exceedingly beneficial to germination, other factors being equal. In the work carried on by Burns already referred to, there are at least two statements that a certain amount of light is necessary for satisfactory germination. Whether he means to imply by the term "light" merely the luminious energy or the heat energy of the sun or both is difficult to say. As a general thing it is impossible to have light energy without a certain amount of heat energy, but heat and light affect plants so differently that the final effect of these factors is easily recognized. It is important to keep these two concepts separate in order to avoid confusion. Graves also makes the statement that light is necessary for the germination of Western White pine. It is inconceivable how luminous energy can play any part in germination, especially when the seeds are below the ground; it is likewise difficult to conceive what possible effect light could habe if it did reach the seed.
