Cryptogamia

Cryptogamia, the name of the twenty-fourth class of the Linnaean classification of plants, implying that in them the process of fertilisation is obscure, is still generally and conveniently employed as a collective name for the three lower sub-kingdoms of the plant world, the Thallophyta, Bryophyta, and Pteridophyta. These plants differ much among themselves in essentials of structure, especially in their vegetative organs, and it is difficult to state positive characters in which they agree. Thus the Thallophytes (algae and fungi) are entirely composed of cellular tissue, generally consist of a thallus, without distinction of stem and leaf, and in many cases possess no process of sexual reproduction. In Bryophytes (mosses and liverworts) and Pteridophytes (ferns, horse-tails, and club-mosses) there is a great contrast in the character of the alternation of generations (q.v.), but there is generally a distinction of stem and leaf, and the two groups agree with one another, and with some of the higher Thallophytes, in having a motile antherozoid (q.v.) as the male element in a sexual process, and in the formation in most cases of minute separable asexual reproductive bodies known as spores or gonidia. From higher plants Cryptogamia are popularly separated as "Flowerless plants," having as a rule no conspicuous clusters of specially modified leaves (perianth) surrounding their spore-bearing leaves or sporophylls, whilst these last but slightly resemble the stamens and carpels of the group called in contradistinction Phanerogamia (q.v.) or Flowering plants. More real distinctions consist in the absence of motile antherozoids in these latter plants and in the formation of that complex reproductive body, the seed, from producing which phanerogams are now termed "spermaphytes." As distinguished from the Thallophytes or Thallogens, Bryophytes and Pteridophytes are sometimes termed Acrogens, having stems growing mainly at their apex, whilst Phanerogams were formerly divided into Endogens and Exogens (q.v.). Again, as distinguished from Dicotyledones and Monocotyledones, Cryptogams were once termed Acotgledones, an inaccurate term, since, though not forming any true homologue of a separable seed with its various coats, the higher Cryptogams do form an embryo with cotyledons, radicle and plumule. Though abandoned by the philosophical student of plant structure, the term Cryptogamia is likely to be long retained in general use, even among botanists, as a convenient term for these three lower sub-kingdoms. Here, however, it is far easier to describe the characteristics of these groups under their separate headings than to state characters common to them all.