CREATION BY EVOLUTION
Early in the development of living things one group of plants acquired the ability to manufacture that wonderful substance, chlorophyll, which gives the green colour to all foliage, and these primitive chlorophyll-bearing organisms must be regarded as the ancestors of all plant life.
_p146_Pleurococcus_vulgaris.png)
Reproduced, by permission, from Gager’s Fundamentals of Botany, published by P. Blakiston’s Sons & Co.
The simplest chlorophyll-bearing plants to-day are the unicellular green algae, such, for example, as Pleurococcus (Fig. 3). These reproduce only by cell-division. Other green algae, such as green silk, or Spirogyra, reproduce by both cell-division and cell-fusion. The introduction of cell-fusion to the life histories of organisms laid the foundation for the development of sex, for cell-fusion is the essential process in sexual reproduction.
The modern representatives of the other great groups of chlorophyll-bearing plants, such as the mosses, ferns, club mosses, little club mosses, and conifers (Figs. 4–7), illustrate definite advances in evolutionary progress, but they do not form a genetical series—that is, they do not bear to each other the relation of ancestor and descendant. Some students incline to the opinion that all the great modern groups of plants have descended from one main hypothetical fern-like branch, the Primofilices, which can be traced back to the dawn of the fossil record but is now extinct. From the Primofilices there descended cycad-like forms (Cycadofilices, cycad-ferns), also now extinct, but known from abun-
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