“Pale primroses
That die unmarried.”—Shakespeare
“Love consumes the plants” once wrote Linnaeus, and the observation of every student of Nature goes to confirm his statement. The plants marry and are given in marriage. Reproduction is undoubtedly their chief end in life.
The simplest and most primitive plants have no sex but produce new individuals by splitting their single cells in two. It is in the thread-like bodies of Pond Weeds that we find the first beginnings of the principle of generation by union. These lowly creatures consist of single cells strung end to end like beads in a necklace. When two of the living chains happen to find themselves parallel to each other, certain of the cells reach out and join those opposite them to form new cells. Such a mixture of life forces is always beneficial to the race.
In the higher plants the same process is carried out in a little more elaborate way. Of the two cells which unite, one is small and active, and is called the male or pollen cell. The other is larger, richer and more passive, and is the ovule or female cell.
It is one of the main objects of each plant’s life to see that its ovules are fertilized by pollen grains from some other member of the same species. When this is impossible, flowers are reduced to fertilizing themselves, but if this continues very long, degeneracy is very apt to result. It is not wise to marry one’s first cousin.
Many plants depend upon the wind to distribute their pollen. Such species bear slight, inconspicuous flowers which not infrequently cluster together in long, pendent catkins. This was undoubtedly the first and original form of plant marriage. Though often successful, it is very wasteful and undependable. “The wind bloweth where it listeth” and loses a million grains of pollen for every one it lodges.
One hazy day in the long ago, some plant had a brilliant idea. “There are a number of insects which are in the habit of paying me unwelcome visits for the purpose of eating pollen. Why can’t I make use of these thieves and turn their marauding habits to my own advantage?”
No sooner said than done, though it doubtless took many centuries to get the plan in thorough working order. It was a new departure in the plant world and led to various revolutionary changes. In all probability, there were no bright-hued flowers before the advent of pollen-eating insects. In the beginning, at least, flowers were developed as the signs by which plants advertised their wares. “We will make ourselves luringly attractive,” reasoned the plants. “We will add to our bright-coloured petals the sweet delights of nectar and honey. While the insect is eating at our table, we will shower his back with pollen and, going forth to some floral neighbour, he will unwittingly become the marriage priest of our race.”
This was the idea, and in many diverse and wonderful ways the plants have carried it out. The first flowers were developed by training certain stamens to flatten and expand themselves, daub their surfaces with colour, and so become petals. This evolutionary fact can be seen today in the white Water Lily, where concentric rows of stamens gradually merge into petals. Double Roses and Poppies are examples of the same thing.
The formation of flowers was only the first step. It is not enough to get the insect to come to the plant. Once he is there, means must be found to make sure that he performs the marriage duties assigned to him. Each flower takes care of this problem in a different way.