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birds, but useful stations for bird watching.
Cultivated varieties of hollies are so popular we hardly feel the need to remind our readers that the group is almost entirely dioecious, that is, there are separate male and female plants in each species.
Both sexes produce similar inconspicuous flowers in the late spring and summer, but a close look will reveal that the flowers on males have aborted pistils and those on females have aborted stamens. Female hollies have dominated this discussion so far—they’re the ones that produce the fruits that are so spectacular in winter. But males are necessary (yes, Virginia, this is a biological fact, at least for hollies) for fruiting to take place on females. They need not be very close to each other, but a male — only one — somewhere in the proximity of females is necessary as a source of pollen.
Dioecy has fascinated botanists since before Linnaeus’ time, and a number of adaptive explanations for the condition have been proposed. Most modem ones are variations on the idea that separating genetic individuals during mating reduces inbreeding and the genetic problems that often accompany this.
However, only about 10 percent of the flowering plants are dioecious, and it is an interesting fact that these are mostly species that produce fleshy, animal-dispersed fruits rather than hard or dry, wind-dispersed types. The adaptive argument for this is that animal dispersal is energetically costly and dioecy results in a reduced cost. For example, females can invest more in fruits if they don’t also invest in pollen.
We don’t know. But it gives us something to think about while we’re waiting for Cedar waxwings at a bnght-red patch of Ilex verticillata!
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