102 MISSOURI BOTANICAL GARDEN. 
tions. The dandelion goes to rest at 5 p. m., and wakes 
at 7 a.m., while the popular names of ‘ 4 o’clock”’ and’ 
** John-go-to-bed-at-noon”’ sufficiently indicate the sleep- 
ing hours of Mirabilis and Tragopogon. Sir John Lubbock 
tritely asks «* What is the meaning of sleep in flowers, if 
it is not in reference to insects?’? The closing during 
those hours when the particular insects needed for pollina- 
tion are at rest, would protect the flower from spoliation 
by useless raiders. This belief is also strengthened by the: 
fact that anemophilous flowers of those fertilized by the 
wind, never sleep, and that flowers which attract insects by 
smell, emit their odor at particular hours. 
But the most interesting fact not commonly understood, 
that has now been very fully established by the most 
thorough researches, is, that a very large number of plants, 
even where the sexes are united in the same flower, abso- 
lutely depend on insect aid for pollination, and that the 
contrivances to induce cross-fertilization are infinite in di+ 
versity, while the modifications in structure which these 
insects have undergone the better to fit them to perform 
this service, are equally remarkable. 
In Dr. Asa Gray’s little work, «* How Plants Behave,’’ etc., 
instances enough are given, in an admirably plain and lucid 
style, to show the manner in which many flowers are cu- 
riously and elaborately constructed so as just not to do of 
themselves what must necessarily be done for them in order 
to prevent degeneracy or extinction of the species. Some 
plants, as Fritz Miller proved, are so self-impotent that 
they never produce a single seed by aid of their own pollen, 
but must be fertilized by that of a supposed distinct 
species, or even of a supposed distinct genus; while in 
some cases the pollen and stigma mutually act on each 
other in a deleterious manner. In most of these entomo- 
philous plants fructification may be brought about by the 
aid of more than one species of insects, and few plants 
offer a more striking instance of dependence or more cus 
rious floral mechanism to allure, than do the orchids. In 
