312 Profs. Percy Frankland and Marshall Ward. 



The following diagram gives the sectional view. 



a = hanging drop, suspended from cover slip forming roof of moist chamber ; b = 

 glass cell in section; c glass slide forming floor of moist chamber; d = layer 

 of water to prevent hanging drop drying up ; e = lower coloured or other glass 

 screen ; f upper ditto, supported on wooden blocks shown in section at gg. 



The glass screens were made sufficiently large to ensure that no 

 light could possibly reach the moist-chamber that had not previously 

 traversed them. 



All being thus ready, the moist-chambers were placed in position, 

 and the upper screen removed while I focussed the contents of the 

 hanging-drop, and arranged so that the mirror of the microscope 

 threw the light directly up, through the lower screen. The tube of 

 the microscope was then drawn up so as to raise the objective suffi- 

 ciently to allow of the npper screen being placed in position. 



All the microscopes thus loaded were placed side by side at a 

 south window, and illuminated exactly alike, and for equal periods ; 

 maximum and minimum thermometers being placed in position by 

 them. 



At stated intervals I examined all the cultures, and measured the 

 growth, &c., of the filaments as follows : In every case a number of 

 filaments usually five to ten were measured, and an estimate 

 formed of the commonest length that prevailed. Then I sought 

 throughout the drop for the longest and for the shortest filament I 

 could find. 



In this way I was enabled to obtain a fair estimate of the amount 

 of increment going on in each culture, as compared with a standard 

 culture kept in the dark ; for numerous trials had shown me that 

 the spores germinate so freely, and the germinal rodlets in any one 

 drop grow so evenly during the early periods, that the method may 

 be trusted at least up to the point I push it to. 



The following experimental series are typical, and serve very well 

 to bring out the instructive results obtained by these comparative 

 cultures. 



To test the relative effects of strong blue and red light on the 

 growth of the germinal filaments, two cultures were made in glass 

 cells, as usual, and placed behind blue and red glass screens respec- 

 tively. 



