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Morphological characteristics of flowers
Angiosperms have heteromorphic spores, and they can also produce two kinds of reproductive spores. Pollen (microspore, male) and ovule (megaspore, female) are produced in different organs, but typical flowers contain both megaspores and microspores because they have two organs at the same time.

If a pedicel has branches and all branches have flowers, then the branches are called petioles. The swollen part at the top of the flower stalk is called the receptacle, and all parts of the flower rotate on the receptacle. The four main parts are from the outside to the inside:

Calyx: The outermost sepals are usually green, but some plants are petaloid.

Corolla: located in the inner wheel of calyx, it consists of petals, which are thin and soft and often colored to attract insects to help pollination.

Stamen group: the general term for stamens in a flower. Anthers are attached to the top of filaments, where pollen is formed. Pollen contains male gametes.

Gynostemma pentaphyllum: the general name of pistils in flowers, which can be composed of one or more pistils. The reproductive organ that makes up the pistil is called carpel, which contains an ovary and ovules (including female gametes).

Flowers are divided into incomplete flowers and complete flowers.

Pistil may be composed of multiple carpels. In this case, if each carpel is separated to form a single pistil, it is called centrifugal pistil, while if carpels are combined, it is called compound pistil. The sticky tip of pistil is called stigma, which is the receptor of pollen. Style connects stigma and ovary, which is the passage for pollen tube to enter ovary after pollen grains germinate. Stamens usually fall off after pollination and fertilization.

For example, two subclasses of angiosperms can be distinguished by the number of petals: dicotyledons usually have 4 or 5 petals (or multiples of 4 or 5), while monocotyledons usually have multiples of 3 or 3. As mentioned above, the flowers of most plants have both pistils and stamens, which are botanically called "complete flowers", "bisexual flowers" or "bisexual flowers". However, there are also some plants whose flowers are "incomplete flowers" or "unisexual flowers", that is, flowers with only stamens or pistils. In this case, if the female and male flowers grow on different plants, they are called "dioecious plants". On the contrary, if unisexual male flowers and female flowers are born in the same plant, it is called "monoecious".

The flowers of some plants are solitary on the plants, while those of some plants are clustered on the plants. For the latter, if these flowers are arranged on the floral axis according to certain rules, they will form "inflorescences". At this point, we must pay attention to the actual concept of "flower". From the botanical point of view, a chrysanthemum or sunflower is not a flower, but a flower head, that is, an inflorescence composed of many small flowers, all of which have the above-mentioned structure. Some flowers have radiation symmetry, that is, if their flowers are divided into two by the central axis at any angle, the two halves are symmetrical and equal, which is called radiation symmetry flowers or neat flowers, such as roses and peach blossoms. Some flowers, such as snapdragon and most orchids, can only be obliquely cut into two symmetrical sides, so they are called left-right symmetrical flowers or irregular flowers. Flowers attract people with their bright colors, graceful posture and fragrant smell. Flowers are actually shortened deformed branches. Like leaves, petals can be divided into epidermis, basic parenchyma and vascular bundles. The epidermis of petals often has protrusions (see the second print), trichomes and pores, and the cuticle on the surface often presents wrinkles and stripes.