The best known of the genera is that of _Cycas_, of which an illustration is given in fig. 74. The thick, stumpy stem and crown of “palm”-like leaves give it a very different appearance from any other Gymnosperm. Commonly the plants reach only a few feet in height, but very old specimens may grow to the height of 30 ft. or more. The other genera are smaller, and some have short stems and a very fern-like appearance, as, for example, the genus _Stangeria_, which was supposed to be a fern when it was first discovered and before fruiting specimens had been seen. The large compound leaves are all borne directly on the main stem, generally in a single rosette at its apex, and as they die off they leave their fleshy leaf bases, which cover the stem and remain for an almost indefinite number of years. The wood of the main trunks differs from that of the other Gymnosperms in being very loosely built, with a large pith and much soft tissue between the radiating bands of wood. There is a cambium which adds zones of secondary tissue, but it does not do its work regularly, and the cross section of an old Cycad stem shows disconnected rings of wood, accompanied by much soft tissue. The cells of the wood have bordered pits on their walls, and in the main axis the wood is usually all developed in a centrifugal direction, but in the axis of the cones some centripetal wood is found (refer to _c_, fig. 65, p. 97). [Illustration: Fig. 74.—Plant of _Cycas_, showing the main stem with the crown of leaves and the irregular branches which come on an old plant] In their fructifications the Cycads stand even further apart from the rest of the Gymnosperms. One striking point is the enormous size of their _male_ cones. The male cones consist of a stout axis, round which are spiral series of closely packed simple scales covered with pollen-bearing sacs (which bear no inconsiderable likeness to fern sporangia), the whole cone reaching 1½ ft. in length in some genera, and weighing several pounds. All the other Gymnosperms, except the Araucareæ, where they are an inch or two long, have male cones but a fraction of an inch in length. [Illustration: Fig. 75.—Seed-bearing Scale of _Cycas_, showing its lobed and leaflike character _s_, Seeds attached on either side below the divisions of the sporophyll.] In all the members of the family, excepting _Cycas_ itself, the female fructifications also consist of similarly organized cones bearing a couple of seeds on each scale instead of the numerous pollen sacs. In _Cycas_ the male cones are like those of the other genera, and reach an enormous size; but there are no female cones, for the seeds are borne on special leaflike scales. These are illustrated in fig. 75, which shows also that there are not two seeds (as in the other genera with cones) to each scale, but an indefinite number.