The spores of ferns are borne on leaves; the spores of seed-bearing plants are also borne amongst a mass of specially developed conspicuous leaves known as =flowers=, therefore these plants have been known as the =flowering plants=. Some of the leaves are developed as envelopes (calyx, corolla), and others as spore-bearing parts, or =sporophylls= (stamens, pistils). But the spores of the lower plants, as of ferns and mosses, may also be borne in specially developed foliage, so that the line of demarcation between flowering plants and flowerless plants is not so definite as was once supposed. The one definite distinction between these two classes of plants is the fact that _one class produces seeds and the other does not_. The seed-plants are now often called =spermaphytes=, but there is no single coördinate term to set off those which do not bear seeds. It is quite as well, for popular purposes, to use the terms =phenogams= for the seed-bearing plants and =cryptogams= for the others. These terms have been objected to in recent years because their etymology does not express literal facts (_phenogam_ signifying “showy flowers,” and _cryptogam_ “hidden flowers”), but the terms represent distinct ideas in classification. The cryptogams include three great series of plants--the =Thallophytes= or algæ, lichens, and fungi; the =Bryophytes= or mosslike plants; the =Pteridophytes= or fernlike plants. [Illustration: FIG. 263.--DIAGRAM TO EXPLAIN THE TERMINOLOGY OF THE FROND.] SUGGESTIONS.--=186.= _The parts of a fern leaf._ The primary complete divisions of a frond are called pinnæ, no matter whether the frond is pinnate or not. In ferns the word “pinna” is used in essentially the same way that leaflet is in the once-compound leaves of other plants. The secondary leaflets are called pinnules, and in thrice, or more, compound fronds, the last complete parts or leaflets are ultimate pinnules. The diagram (Fig. 263) will aid in making the subject clear. If the frond were not divided to the midrib, it would be simple, but this diagram represents a compound frond. The general outline of the frond, as bounded by the dotted line, is ovate. The stipe is very short. The midrib of a compound frond is known as the rachis. In a decompound frond, this main rachis is called the primary rachis. Segments (not divided to the rachis) are seen at the tip, and down to _h_ on one side and to _m_ on the other. Pinnæ are shown at _i_, _k_, _l_, _o_, _n_. The pinna _o_ is entire; _n_ is crenate-dentate; _i_ is sinuate or wavy, with an auricle at the base; _k_ and _l_ are compound. The pinna _k_ has twelve entire pinnules. (Is there ever an even number of pinnules on any pinna?) Pinna _l_ has nine compound pinnules, each bearing several entire ultimate pinnules. _The spores._--=187.= Lay a mature fruiting frond of any fern on white paper, top side up, and allow it to remain in a dry, warm place.