202 TOWARDS THE HUMAN FORM 



plants results from the multiplication of a single initial cell, 

 the ovum, so their general form is actually achieved by the 

 successive multiplications of leaves, beginning with two, or 

 even one. 



Bernard Renaud discovered the presence in coal-seams of 

 monocellular Micrococci, already attacking the cellulose, as the 

 Bacillus amylobacter does to-day. On account of their fragility 

 the Algae, Hepaticae, and Mosses have rarely been preserved 

 in a fossil state, so that the forms by which vascular Cryptogams 

 (Horse-tails, Club-mosses, Ferns), the first plants with roots, 

 detached themselves from the Algae or the Mosses, is still 

 hidden from our knowledge. From that point, however, all is 

 clear — everything happened in conformity with the conditions 

 indicated by the law of tachygenesis. Grand'Eury has estab- 

 lished the formation of veritable ovules evolving into seeds in 

 plants — Pteridosperms, which are Gymnosperms in this 

 respect, though still Ferns so far as their leaves are concerned. 

 The Gymnosperms (Cordaiteae, Conifers, Gnetaceae, Cycads) 

 associated with the vascular Cryptogams are the only 

 terrestrial vegetable forms of the Primary and the 

 Triassic Periods. In the Jurassic certain questionable Angio- 

 sperm forms alone are known, and it is not until well into 

 the Cretaceous that we see such plants definitely flourishing. 

 While the Conifers among the Gymnosperms were multi- 

 plying vigorously, Dicotyledons were abundant, but they were 

 chiefly represented by small-flowered plants, generally uni- 

 sexual and with the flower arranged in catkins something after 

 the style of the cones of the Conifers. These were Poplars, 

 Willows, Birches, Myrica with male flowers often reduced to 

 one or two stamens, Beeches, Oaks, Walnuts, Figs, Bread-fruit, 

 Credneria, Plane-trees, Liquid-ambars, and Maples, to which 

 were added a few flowering plants : Ivy, Dogberry-tree, 

 Laurel, Saxifrage, etc. To these small-flowering Dicotyledons 

 were already added a few Gamopetalous plants, such as the 

 Viburnum and Oleander. 



Next to the Dicotyledons with small unisexual flowers, the 

 oldest plants must be those in which the flower-parts, still very 

 numerous, have retained the helicoidal arrangement of the 

 Conifers and in which the sepals are often transformed gradually 

 into petals and the petals into stamens. These are the Magno- 

 liaceae, the Nympheaceae, Cacti, Ranuculaceae, Rosaceae, 



