62 THE PLANT WORLD. 



elsewhere they are absent. Old floral wreaths are allowed to 

 accumulate in the balcony of the church. 



PARAFFINED WIRE POTS FOR SOIL CULTURES. 



By Burton Edward Livingston. 



Everyone who has ever attempted to grow seedlings or cut- 

 tings in small pots of the ordinary form has observed the fact that 

 the first roots developed under these conditions penetrate rapidly 

 through the soil to the wall or bottom of the pot and then develop 

 against its inner surface, often forming a dense weft of branches 

 in this region before any considerable branch growth has oc- 

 curred within the soil mass itself. It is rarely possible in these 

 pots to obtain such a uniform distribution of the root system as 

 is produced b}- the same plants in the open soil, where, under 

 normal conditions of moisture, the root branches radiate uni- 

 formly, and by binding the soil grains together, produce the 

 familiar ball of earth which clings so tenaciously to small plants 

 lifted from the open ground. 



This peculiar l:ehavior of the roots of potted plants is probably 

 due to the unusual condition existing where soil and pot come in 

 contact. There is often an appreciable opening between the pot 

 and its contents through which air changes can take place much 

 more rapidly than through the pore-spaces of the soil itself, and 

 it is certain that in such pots there is always a better opportunity 

 for gas diffusion along this surface of contact than elsewhere in 

 the pot. Besides this, the porosity of clay pots allows diffusion 

 of gases directly through the walls and may also exert an in- 

 fluence on the growth of the plants through evaporation on the 

 external surface and the accompanying movement of water from 

 Avithin outward. Whether the outward growth of the first roots 

 is a phenomenon of aerotropism or not, it seems quite probable 

 that the greatly accelerated growth and production of branches in 

 the vicinity of the walls is largely due to the better aeration in 

 that region. 



