TRANSACTIONS OF THE SECTIONS. 57 



of the spectrum, are enumerated in the table annexed, by reference to which it 

 will be at once seen, what specific luminous influence was exerted upon the seeds by 

 each of those coloured glasses or fluids which are named in the brief statement of the 

 experiments which follow. /-> /• j p 



I am indebted to Mr. Maskelyne, the Deputy-Reader of Mmeralogy at Oxford, tor 

 having examined the various media employed, and dettned by reference to Frauen- 

 hofer's lines the exact quality of the rays transmitted by each, as is stated m the 

 Table. (See Plate VI 



In the first set of experiments a south aspect was selected, and the following seeds 

 were experimented upon, viz. — 



Datura Catiila 10 Helianthus annuus 13 



Malope grandiflora M Polygonum fagopyrum 16 



Trifolium incarnatum 14 Hordeum sativum 14 



Raphanus rotundus 12 



^ In all 93 



But as none of the two first came up, the real number operated upon may be esti- 

 mated at 69. Of these — 



46 radicles and 18 plumules came up under violet light. 

 44 radicles and 18 plumules came up under green glass. 



41 radicles and 19 plumules came up in one instance \^^ darkness. 



41 radicles and 5 plumules came up in another instance J 



36 radicles and 26 plumules came up under cobalt-blue glass. 



32 radicles and 17 plumules came up imder amber glass. 



29 radicles and 7 plumules came up under ruby glass. 



23 radicles and 5 plumules came up under orange glass. 

 Accordingly, in this series a slight superiority seemed certainly to belong to the violet- 

 coloured medium over the rest, in relation to the number both of radicles and of 

 plumules which appeared; whilst in respect to the quickness of their germination, the 

 violet and green media were a-head of the rest, although the plumules did not follow 

 the same order. 



When, however, the same experiments were repeated in a north aspect, the same 

 law did not hold good, for out of 69 seeds, — 



52 radicles and 22 plumules appeared under green glass. 



49 radicles and 17 plumules appeared under blue glass. 



47 radicles and 14 plumules 1 ^ed in darkness. 

 47 radicles and 21 plumules J ^^ 



44 radicles and 1 7 plumules appeared under transparent glass. 



39 radicles and 23 plumules appeared under violet light. 

 And with respect to the quickness of germination, it appeared that the green stood first 

 in order; that the seeds luider blue and violet glass and in absolute darkness came 

 up next in order, and with nearly equal rapidity ; that those in full light were next 

 in order ; whilst orange, ruby, and yellow were about equal, but somewhat later than 



the rest. i. • i v -u 



It did not appear, therefore, from this last series of experiments, that violet light 

 favoured germination at all more than any other species of light ; nor indeed that any 

 kind of ray was injurious to the process, so long as its intensity was not too great, as 

 maybe inferred to have been the case in the first set of experiments, where the seeds 

 were exposed to the full rays of the sun in a southern aspect. 



I therefore, in my subsequent experiments, selected uniformly a north aspect for 

 the germination of the seeds ; and in order still further to test the point as to whether 

 the quality of the light had anything to do with the process, I placed as before upon 

 the surface of the soil, in boxes, ten seeds of each of the four following plants, viz. 

 peas, beans, kidney-beans, and a species of sunflower (^Helianthus annuus), all of which 

 germinated. Now in this case 



37 radicles and 25 plumules appeared in the dark box ; 



36 radicles and 30 plumules appeared under green glass; 



35 radicles and 30 plumules appeared under blue glass ; 



34 radicles and 24 plumules appeared under transparent glass; 

 the whole number of seeds operated upon being only 40. 



