CH. VIIl] DROSERA. 209 



solution and 10 others with the distilled water used in 

 making the solution. In each glass place a healthy leaf, 

 and examine them after an hour, when the phosphate 

 leaves should show much inflection, whereas only a few 

 isolated tentacles in the control leaves ought to have 

 moved. A longer period than one hour may be required 

 in some cases. 



(241) Drosera: asymmetrical inflection. 



If a particle of raw meat, or preferably a minute frag- 

 ment of calcium phosphate, is placed in the middle of a 

 leaf the exterior tentacles all bend towards the centre. If 

 however the object is excentrically placed, e.g. halfway 

 between the centre and circumference of the disc of the 

 leaf, the tentacles no longer bend symmetrically towards 

 the centre, but are plainly directed towards the phos- 

 phate 1 . 



(242) Berberis (Mahonia) aquifolium : irritable stamens*. 



The flowers do not easily lose their irritability; cut 

 twigs in water may be used, or even isolated flowers, if 

 only moderate care is used to prevent them withering. 

 Some of the larger flowered species are more convenient 

 to work with than those of B. aquifolium. 



In the condition of repose the anthers lie in the bifid 

 hoods of the petals : when the filaments are irritated they 

 curve inwards, bringing the anthers close up to the 

 stigma. To localise the irritable part, the anther should 



1 See Insectivorous Plants, Fig. 10, p. 24-1. 



2 Heckel, Comptes rendus, 1874, Vol. 78. 



D. A. 14 



