The British flora is singularly poor in coniferous plants, the Scots Pine, the Yew, and the Juniper being our only native species, and even of these some authorities will have it that the Yew is not truly a Conifer at all; they place it in a separate order--_Taxaceae_. For our present purpose, however, although the Yew does not produce cones, it will be convenient to keep it in its old position. The principal feature distinguishing all Conifers and their allies (_Gymnosperms_) from other flowering plants (_Angiosperms_) is briefly this: Angiosperms have their incipient seeds (_ovules_) enclosed in a carpel, through which a shoot from the pollen grain has to penetrate in order to reach and fertilize the ovule. In Gymnosperms the carpel takes the form of a leaf or bract, upon which the naked ovule lies open to actual contact with the pollen grain. After fertilization the carpel enlarges to protect the seed, and becomes fleshy or woody, in the latter case a group of carpels forming the well-known cones of Pine or Fir. [Illustration: _Pl. 73._ Yew.] In some of the groups (as the Yew, for example) the male or pollen-producing flowers are borne by a separate tree from that which bears the female or cone-producing flowers. In the Pines both sexes are found on the same tree; but throughout the order the pollen is carried by the wind. All the species are trees, or shrubs. They are among the most valuable of timber trees, and, in addition, yield a number of useful substances, such as pitch, tar, turpentine, etc. The leaves are always rigid, extremely narrow, and long in proportion: usually of the form that botanists term linear, with the two sides parallel. In the Yews these leaves spread out in two rows from opposite sides of the twigs; in the Pines they are in clusters of two, three, or five, seeming to be bound together at the base by a wisp of thin skin. The number of leaves in each bundle is often a help in distinguishing species.