THE USE OF GLASS POTS. 15 



vention of an obscuring green growth of microscopic algse required 

 some arrangement for keeping the light away. This was accom- 

 plished either by sinking, or, as gardeners say, " plunging," the pots 

 nearly to the rim in sand, moss, or soil, or, when the pots were not 

 plunged, by fitting closely to the outside of each a removable cuff, as 

 it were, made of the opaque gray blotting paper used in pressing 

 specimens of plants. The use of a pot with transparent walls was 

 found to be of very great importance in the study of these plants, for 

 plants identical in appearance so far as the parts above ground were 

 concerned sometimes showed the most pronounced differences in the 

 growth and behavior of the roots, differences which otherwise would 

 not have been observed but which were in reality responsible for the 

 conspicuous changes that later took place in the growth of the stems 

 and leaves. The use of such glass pots, drained and darkened, is 

 strongly recommended to plant experimenters who use pot cultures, 

 as they afford a means of acquiring easily an intimate knowledge of 

 the great variations in the behavior of the feeding organs, the roots, 

 under different conditions. 



On December 22, 1908, six glass pots were filled with the garden 

 soil described above, and a seedling blueberry about an inch in height 

 was transplanted into each. The seed bed from which the seedlings 

 were taken had been allowed to become partially dry before the 

 transplanting was done. In this condition there was no difficulty in 

 removing all of the sandy soil adhering to the roots of a seedling, so 

 that after it was transplanted it must derive its soil nourishment 

 from the new soil exclusively. In potting, the roots of the plant 

 were laid against the glass on one side of the pot so that their 

 behavior could be observed from the very first. 



A transplanting of six other plants was then made, similar in all 

 respects to the first except that the soil used was a peat mixture known 

 from earlier experiments to be productive of vigorous growth in 

 blueberry plants. The exact character of this soil will be discussed 

 later in this publication. 



This peaty blueberry soil is ill suited to the growth of ordinary 

 plants, while in the garden soil ordinary plants flourish luxuriantly. 

 In order to bring out this fact clearly by an experiment six glass pots 

 containing this garden soil were planted with five alfalfa seeds each, 

 and six more with one rooted rose cutting each. An identical 

 planting was made in twelve pots of blueberry soil. 



Average examples of the growth that took place in these plantings 

 are shown in figures 1 to 6, reproduced from drawings carefully made 

 from actual photographs. In the garden soil the rooted rose cut- 

 ting, which was of the variety known as Cardinal, made vigorous 

 growth of both root and stem, and in forty-four days, when the 



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