AS PROTECTIVE AGAINST RADIATIOX. G27 



were laid on cork with their leaflets naturally conduplicate or 



otherwise protected as in nature. In the morning I weighed each 



group again, and reduced their losses to percentages of the original 



weights of each group respectively. I found that there was in 



every case a generally much greater loss in the case of the leaves 



artificially exposed than with the others, as will be seen from the 



following examples : — 



Loss p. c. Loss p. c. 



Laurustinus, exposed naturally 87. Spread out, 18'7 



Portugal Laurel „ „ 8-4 „ 126 



Lime „ n 4-5 „ 214 



Laburnum „ „ 14-8 ,, 330 



Ash „ 23 „ 118 



Pose „ 10(5 „ 176 



Periwinkle „ , 5-0 „ 1205 



Clover „ „ 244 „ 293 



Walnut „ „ 187 „ 246 



Very few nights of the last month (May) were frosty, so that 

 several attempts to carry out experiments were unsatisfactory, as 

 so many nights were cloudy, windy, and stormy, and ill-suited for 

 radiation ; yet on one occasion, when about three degrees of frost 

 occurred, the Walnut, Lime, and Laburnum leaves when spread 

 out showed to the eye unmistakable injury ; whereas these three 

 kinds of leaves, placed as they occur on the trees, did not appear 

 to be hurt. Other leaves treated in the same way and subjected 

 to the same slight frost did not appear to have suffered ; but I 

 had not at that time thought of weighing them. 



I will now add a selected series to illustrate the various methods 

 adopted whereby the young and developing leaves are protected 

 from injury by radiation. 



I. Simple Leaves. (1) Opposite : (i) erect.— This position is 

 assumtd in all cases of opposite leaves which I have had an 

 opportunity of examining. The leaves face one another with 

 their upper surfaces more or less in close contact, concealing the 

 bud between them. Iu shrubby Veronicas and Hypericums and 

 Periwinkle the leaves are almost, as it were, glued together, so 

 firmly do they cohere all round the margins. In others, such as 

 Aucuba and Laurustinus, they are more slightly adjusted. The 

 only exceptions that I have met with were Snowberry, Weigela, 

 Honeysuckle, and the leaflets of the Elder, all being of the same 

 family, Caprifoliace* *. The pairs of leaves had their edges iu- 



* I first discovered this difference in Weigela,aaA that led me to examine the 

 others, which revealed the fact that this peculiar form of vernation is an ordinal 

 character. 



