So-called Excretions not Useless. 135 



namely, tliat the- organs which serve to attract insects 

 shall suspend their activity for a time, or, in other 

 words, that the function of attraction shall be in abey- 

 ance throughout the day. This literally happens in 

 the flowers of the above-named CaryophyUacese, which, 

 during the daytime, display only the dirty and incon- 

 spicuous under-side of their petals, and exhale no per- 

 fume. 



It is evident that this arrangement is not without 

 its due result. For, as already remarked, these flowers 

 are much frequented by such flying insects as are 

 active in the evening and in the night, but remain 

 entirely unnoticed and unvisited by the numerous 

 species that buzz about in sunshine ! 



8. Diversion of Visitors from the Flower. 



Though we are doubtless justified in calling the 

 substances discharged by glandular cells, or groups of 

 cells, " excretory matter," yet this designation is only 

 true in a certain sense, and must not be supposed 

 to imply that the substances are of no use to the 

 plants, and that after they are once discharged they 

 possess no further functional significance. The obser- 

 vations recorded in the preceding pages show with 

 abundant sufficiency how important a part may be 

 played by these so-caUed excretions ; and I would here 

 only add the remark that even the oxalate of lime, 



