386 



Dr. W. J. Russell. The Action of 



[June 19, 



been found to be the case, and the action has been traced from its commence- 

 ment in the sprouting embryo of a plant till after its death. Postponing for 

 the present the full discussion of the cause of this activity of vegetable 

 matter on a photographic plate, it may be assumed as a working hypothesis 

 that the active substance is hydrogen peroxide. As far as the activity 

 of a plant goes, it is comparable with that of hydrogen peroxide. For 

 instance, if one part of pure peroxide be dissolved in one million parts of 

 water it is sufficient to enable the solution in 24 hours at ordinary tempera- 

 tures, even when the plate is §■ inch above the liquid, to give a marked action 

 on the plate ; and, on the other hand, a seed leaf of a runner bean weighing 

 only 0*02 gramme can give a similar effect. 



Taking now the case of a bean, both the broad and the runner bean act in 

 the same way ; the cotyledons when tested by bringing them in contact with 

 the photographic plate, either whole or in a crushed state, are always found 

 to be quite inactive ; the plumule and radicle before growth has begun is also 

 without action, and even when growth has just commenced and the plumule 

 lengthened 2 or 3 mm. it is still apparently unable to act on a plate, but as 

 soon as plumule and radicle have increased in length about 15 to 20 mm., 

 then it has become distinctly active. The following experiments illustrate 

 this point : — 



A plumule and radicle 8 mm. long, taken from a dry bean, was entirely 

 inactive. Another bean which had been in moist sand for four days, and 

 was 13 mm. long, and just beginning to grow, was still unable to act on 

 a photographic plate, but in another case in which the plumule and radicle 

 had grown to the length of 19 mm. there was a faint action on the plate, and 

 where the growth had extended to 80 mm. the liquid from this plant was 

 distinctly active, and lastly, a young bean plant, 170 mm. long, contained 

 a liquid which was very active. The cotyledons remain always quite 

 inactive. Wheat in its ordinary dry condition is without action on a plate, 

 but if allowed to sprout by being placed in moist sand for about two days 

 the shoots on being squeezed between paper show considerable activity. 

 In fact, it appears that all seedlings contain in every part, plumule, radicle, 

 and seed leaves, a juice which is capable of acting on a photographic plate. 

 If seedlings be grown in the dark they still have this power. 



In addition to the bean and wheat, other seeds and fruits have been 

 experimented with, specially acorn, horse chestnut, pea, barley, almond, and 

 many others, and the conclusion is that in their embryo state they are 

 devoid of all power of acting on a photographic plate, but that as soon as 

 growth commences this power appears. 



Supposing, as has more than once been suggested and is strongly urged by 



