The young roots of these plants have a very characteristic cortex, which consists of cells loosely built together in a lacelike fashion, with large air spaces, so that they are much like water plants in their appearance (see fig. 108). Indeed, so unlike the old roots and the stems are they, that for long they were called by another name and supposed to be submerged stems, but their connection with _Calamites_ is now quite certain. As their woody axis develops, the secondary tissue increases and pushes off the lacelike cortex, and the roots become very similar in their anatomy to the stems. Both have similar zones of secondary wood, but the roots do not have those primary canals which are so characteristic of the stems, and thereby they can be readily distinguished from them. The fructifications of the Calamites were not unlike those of the living types of the family, though in some respects slightly more complex. Round each cone axis developed rings of sporophylls which alternated with sterile sheathing bracts. Each sporophyll was shaped like a small umbrella with four spokes, and stood at right angles to the axis, bearing a sporangium at each of the spokes. A diagram of this arrangement is seen in fig. 109. [Illustration: Fig. 110.—Longitudinal Section of Part of _Calamites_ Cone _br_, Sterile bracts attached to axis; _sp_, attachment of sporophylls; S, sporangia. At X a group of four sporangia is seen round the sporophyll, which is seen at _a_. (Microphoto.)] A photograph of an actual section of such a cone, cut slightly obliquely through the length of the axis, is seen in fig. 110, where the upper groups of sporangia are cut tangentially, and show their grouping round the sporophyll to which they are attached. A few single tetrads of spores are enlarged in fig. 111, where it will be seen that the large spores are of a similar size, but that the small ones of the tetrads are very irregular. They are aborting members of the tetrad, and appear to have been used as food by the other spores. In each sporangium large numbers of these tetrads develop and all the ripe spores seem to have been of one size. In a species of _Calamites_ (_C. casheana_), otherwise very similar to the common one we have been considering, there is a distinct difference in the sizes of the spores from different sporangia. The small ones, however, were only about one-third of the diameter of the large ones, so that the difference was very much less marked than it was between the small and large spores of the Lycopods.