76 
Adams .— The Effect on Certain Plants of 
sunlight proved that assimilation proceeded uninterruptedly, the minimum 
occurring at midnight, at the time of least illumination. 
He also concluded (10), from observations made upon the influence of 
diffuse light on flowers, that the flowers were less brilliant in colour and 
fewer in number, and the fruits were smaller in diffuse light than in direct 
illumination, while very diffuse light made the formation of flowers 
impossible. 
Bailey (6), using a protected electric arc light during half the night, was 
able to hasten the development of lettuce in a greenhouse by two weeks. 
Vochting (7) proved that under a weak illumination the formation of 
flowers in numerous phanerogams was either entirely prevented or only 
incompletely achieved. He found that the formation of flowers was closely 
connected with the activity of the leaves. 
Bonnier ( 9 ) found, as the result of exposing plants to continuous electric 
light, that there was a much greater development of chlorophyll as well as 
other internal differences. 
Pfeffer ( 12 ) states that 4 within certain limits, a decrease in the illumina¬ 
tion produces an accelerated rate of growth in a phototonic plant and an 
increase a diminished rate’. 
On the other hand, Macdougal ( 13 ) appears to take a different view. 
He says: ‘The same results have been attained in another form by the 
exposure of growing plants to continuous exposure to electrical illumination, 
or to an illumination in which daylight was supplemented by nocturnal 
illumination from electric arcs, or flames. In all such instances the amount 
of growth, as indicated by the length of the shoots and of the separate 
members, was greater than under ordinary conditions of alternating daylight 
and darkness. If light exerted a direct retarding, or paratonic, influence 
upon the processes of growth, such results would be impossible.’ 
Schimper ( 14 ), speaking of the action of continuous light during 
summer, states that it has a retarding action on growth, but furthers 
assimilation and the formation of pigments and other substances. He 
further states that growth in length of stems and roots is at its optimum 
when light is totally excluded. 
Regarding the action of light on the development of flowers, Schimper 
continues: ‘ The minimum of light for the formation of flowers is lower for 
shade plants than for sun plants ; yet the former generally produce fewer 
flowers than do the latter. The interior of a forest is poorer in flowers than 
a meadow, and certain regions with intense or prolonged illumination, 
such as the higher regions of vegetation in mountains, polar countries, 
and many deserts, are characterized by a great abundance of flowers. 
In such cases, however, other factors co-operate.’ 
Osterhout ( 15 ), commenting on the stunted stems of plants growing at 
high altitudes, states that ‘ the plants in question are comparatively warm 
