It should be noticed, also, that two kinds of pollination are possible. The pollen may be transferred to the stigma of its own flower, or it may be carried to the stigma in some other flower, and this other flower may be some distance away. The former method may be called self-pollination, the latter cross-pollination. It seems evident that flowers in general have made every effort to secure cross-pollination. This would seem to imply that it is a better method for some reason, although we may not be able to explain why. Apparently, however, while flowers in general have tried to secure cross-pollination, they have not entirely abandoned the chances of self-pollination, so that if one should fail the other may be used. In this way it will be found that a great many plants have two kinds of flowers, the ordinary showy kind, and in addition to them inconspicuous flowers which are never seen except by those acquainted with their presence. For example, in the common violet, in addition to those flowers with which everyone is familiar, others are developed which are concealed by the cluster of leaves, which never open, but which are able to produce very well developed seeds. With nectar and pollen provided as food, and with odor and color notifying the insects of their presence, it remains to be noted that the suitable insects are those which fly. A creeping insect is of no avail in the work of pollination, since the pollen will be rubbed from its body as it crawls from one flower to the next. How the flowers ward off the visits of creeping insects, which are attracted as well as the flying ones to the food provided, will be described in a subsequent paper.