climbing birds (e.g., parrots, woodpeckers). The first
and fourth toes are directed backward, while it is the
second and third that are forward.zygomorphic Flowers that are bilaterally symmetri-
cal; can be bisected into similar halves in only one
plane, thereby forming mirror images.zygospore A structure that forms in fungi from the
diploid zygote. It forms sporangia, where meiosis takes
place and forms spores.zygote When male (sperm) and female (ovum)
gametes combine, they form a zygote that develops into
an embryo. The zygote is a diploid cell created by the
fusion of the mature male and female gametes, each of
which has a haploid set of chromosomes (23 in
human). Upon fusion, the zygote has two copies of
chromosomes, one from each parent. It is the fertilized
egg before it starts to divide and grow.356 zygomorphic
Viola cordata,an example of a zygomorphic flower from Virginia.
(Courtesy of Tim McCabe)