What Is a Spore?

A flowering plant makes a new plant by means of a seed. Plants that don't have flowers make a new plant by means of a spore.

A spore is a one-celled organism. It is invisible to the eye and can only be seen under a microscope. There are spores in the air all around us. That's why when food is left exposed, and moulds and mildews form on it, we know where they came from. Some types of spores that were in the air settled on the food and began to grow. 

Some of the plants that reproduce by means of spores are mush-rooms, ferns, and mosses. The algae that live in water also produce spores.

 A plant carries its spores in cases that are called sporangia. in a mushroom, the sporangium is inside the gills beneath the mushroom cap. In mosses, the spores are carried in a capsule at the top of the stalk.

When the spore case is ripe, it opens, and the ripe spores are released. Since they are finer than dust, the wind scatters them far and wide. In the case of water plants, such as the algae, the spores can actually swim away. They have tiny tails called cilia. These spores are called zoospores, and when the ripe case opens, the zoospores swim away quickly. After a short time they come to rest and lose their tails. Then they begin to grow into new plants.

Some spores reproduce by cell division. They grow by pushing out a germ tube through a thin place in the cell wall. The germ tube branches into a mass of threads out of which the new plant grows. This is called asexual reproduction, because differentiated male and female cells are not needed for reproduction to take place.

Other spores are specialized male and female cells. In order to start a new plant, one male and one female cell must join to form a fertilized egg. Some plants alternate in the kind of spores they produce, asexual in one generation and sexual spores in the next.