lo(5 MASS. EXPERIMENT STATION BULLETIN 277 



ill tlie course of the five-month period when tliis test of durability of the pots 

 was under way. 



Wlien the fillers of the pot were j)ro))erly w ater-jiroofed with a substance 

 that had some degree of permanence, it was found that as good plants could 

 be grown in the paper pots as in the glass containers; and the latter in turn 

 were frequently superior to plants grown in the standard clay pots. The re- 

 sults of such a test are shown in Figure 1. 



The Bakelite-treated paper gave excellent results as measured in growth. 

 This substance is not adaptable to the machinery used in treating this partic- 

 ular paper, but it served to demonstrate the improvement obtained in pajier 

 pots when the fibers are properly protected from decomposing organisms. 



It was further learned that a properly coated paper disc in the bottom 

 of a paper pot improved the growth of plants. These discs serve to prevent 

 tiie roots from passing through the cracks in the base of the pot. These cracks 

 result from the folding of certain parts in forming the bottom of the pot. Of 

 the 10 best growing pots in a series of 40, 3 were of glass, 5 were of paper 

 with double coatings of varnish or lacquer and with discs, 1 was of paper 

 coated with Bakelite, and 1 of paper with a double coating of lacquer. It 

 is possible that the discs, by making a more solid bottom, prevent the leaching 

 out of certain nutrients, particularly nitrogen. If the paper pots are set on 

 beds of soil, sand, or cinders, these discs prevent the penetration of the roots 

 into such a moist medium. If the discs are not present, the pots must be 

 lifted frequently to break off these roots, otherwise the major part of the 

 root system will get into the moist bench and be lost when the plant is moved 

 to a new location. 



The most practical paj^er pot was one in which the fibers were im- 

 pregnated and bound together with asphalt. In subsequent tests with several 

 different plants, this paper pot has proved capable of growing as good plants 

 as are produced in clay pots. In Figure 3 are shown the results obtained 

 with tomato, pepper, and calendula plants growing in three-inch pots of clay, 

 jiaraffined pa})er, as])lialt jiaper, and jelly glasses. 



The asphalt paper pot may be profitably used by amateur plant growers 

 who do not have greenhouse facilities. Commercial growers may find these 

 pots of value for the last transplanting as the plants are then potted for 

 shipping, thus eliminating the extra weight and breakage that would occur 

 if clay pots were used. 



Glass Containers as Flower Pote 



The use of glass or vitreous materials in making flower pots, has a prac- 

 tical value. These containers promote good growth of plants in atmospheres 

 of low humidity. In homes, offices, and arid areas of the country, such plan*: 

 containers conserve the moisture in the soil, retain all the nutrients, and 

 considerably reduce the time necessary for the care of plants. 



The prevailing idea that flower pots must be porous is quite erroneous. 

 In practically all laboratories, where plants are grown under controlled con- 

 ditions, non-porous containers of metal or crockware are employed and no 

 question has ever been raised that the lack of porosity of the container has 

 vitiated the results of the experimental work. Unlike the porous pot, the glass 

 container can not eva^iorate moisture on the outside surface. Unless care is 

 exercised in watering, there is grave danger that the soil will be flooded by 

 over-watering; but this may be guarded against by potting the plant with 



