Second Report Upon Electro-Hoeticulture. 209 



were from fifteen to eighteen feet from the lamp, in rather weak 

 light. The first bloom appeared just four weeks after the starting 

 of the light, and it wajs in the light house. For a month or six 

 weeks thereafter the lighted plants bloomed more profusely; but 

 at that time the dark-house plants began to surpass the others, 

 both in numbers and size of flowers and vigor of plants. In other 

 words, the lighted plants bloomed earlier and never made such 

 stocky plants, and they soon exhausted themselves. It is possible 

 that they would have endured longer if' they had been established 

 in the beds for a longer period before the light was put upon them. 

 When do the plants grow ? — It is thought that plants grow 

 mostly at night, using the materials which they have manufac- 

 tiu"ed during the hours of sunlight. The question then arises 

 when the lighted plants grew. Did they grow more rapidly than 

 the others during their fewer hours of darkness, or did they grow 

 when the electric light was burning ? We have made many tests 

 with auxanometers — instruments which measure and record the 

 perodical growth of the plants. The most important fact which 

 these readings have shown is that lettuce plants, under normal 

 conditions, grow about as much in daylight as in darkness; and 

 the periodicity of growth was very irregular. Lettuce leaves were 

 found to grow more rapidly in the light house for the first week or 

 so, 'at which time growth became greater in the dark house. That 

 is, the leaves matured more quickly under the light. The accom- 

 panying records show this. These are the records of the growth 

 of a single leaf upon a well established plant in each house during 

 four consecutive days, the leaf in each case being an inch and a 

 half long when the test was begun. The measurements are here 

 recorded in sixty-fourths of an inch, only the numerators being 

 used: thus four means four-sixty-fourth inch. The four hours dur- 

 ing which the light ran are shown by asterisks in the third column, 

 and whatever gain the lighted plants made over the others is 

 shown by asterisks in the following column; it is therefore appar- 

 ent at a glance what relation such increase bears to the hours of 

 the artificial lighting. 



27 



