835 



plate-iron cjlindre jackt;t. Bj its aid the leinperaiiii'c can be easily 

 kept constant to within 0°.0]. 



The teniperatnre is determined by a platijiuni resistance thermo- 

 meter, which is inserted in a Wheatstone bridge formed by a 

 IIartmann and Braun resistance box. The galvanometer is a Hartmann 

 and Braun mirror galvanometer. The image of the incandescent rod 

 of a NERNST-lamp is thrown l)y a mirror and a lens on a large 

 scale fastened on the wall. The sensitiveness of the instrument is 

 such that a deviation of 0°.01 corresponds with a deviation of about 

 6 cm. on the scale. So it can be seen all through the room whether 

 the temperature remains constant, resp. how much it changes. The 

 indication of the thermoscope inside L is thi'own on this screen i]i 

 the same way (only the NERNST-burner has here two incandescent 

 rods to distinguish it). Accordingly the observer, who is engaged 

 with the pressure balance or some other part of the apparatus, can 

 ascertain from far whether the stationary state has set in. 



The resistance thermometer is gauged with the same leads and 

 in the same bridge arrangement as that with which the measurements 

 take place. For this purpose it is placed by the side of the chief- 

 temperature-normal of the laboratory in a tube flUed with oil in the 

 thermostat which surrounds the vessel .1; the temperature is here 

 kept constant in the ordinary way. 



Amsterdam. Physical Lab. of the University. 



Botany. — ''Experiments on Hybridisation with Canna indica." 

 By J. A. Honing. (Communicated by Prof. F. A. F. C. Went.) 



(Communicated in the meeting of January 31, 1914). 



Among the plants which my Javanese gardener planted in the 

 beginning of 1910 in order to make the empty space round the 

 house look somewhat like a garden, there were two varieties of 

 Canna, which occurred as escapes on the high bank of the Deli river. 

 One of them had leaves entirely green, greeji bracts, a green stem, 

 small red flowers, with yellowish labellum and fruits, which in an 

 unripe condition are green. This variety completely corresponds to 

 the plants, grown fi-om seeds, which I received as Canna indica 

 fi'om the Botanic gardens of Buitenzorg. The other had somewhat 

 darker leaves with a red edge and the flowers were also of a some- 

 what darker red. Further the stem was dark red as were the conical 

 papillae on the unripe fruits. 



