EXTINCT SEED-PRODUCING FERNS 117 



veloped in a variety of ways in different instances and 

 is arrested for a time, often a very long time, in its further 

 growth. The envelopes may be big or small, whilst the 

 living germ within sometimes minute, sometimes big, as 

 in the bean, and bigger still in the cocoa-nut is further 

 protected and assisted in its dispersal by the swelling up, 

 around the seeds, of the substance of the carpels or big 

 spore-bearing leaves, to form the "fruit." Nothing like 

 a seed (that is, a true seed in the botanical sense), nor 

 anything corresponding to a fruit is developed in true ferns, 

 but there were ancient ferns (in the coal-measures) which 

 are shown by well-preserved fossils to have produced 

 attached "seeds" instead of detached prothalli, and consti- 

 tute a group called "seeding ferns." They lead on to 

 primitive cycads (so-called fern-cycads) and primitive coni- 

 fers in the succeeding Oolitic age, from which our modern 

 flowering plants and pine trees have finally arisen. Our 

 ferns of to-day often attain the size of trees (the tree-ferns 

 in Australasia are 50 feet high), but they remain at the 

 lower stage of elaboration of the reproductive process. The 

 extinct "seeding ferns" formed the step leading on to 

 further changes, and they have left no survivors of precisely 

 their own grade of development. The gradual develop- 

 ment of the flower and the fruit followed in their offspring 

 by steps which have been very largely ascertained in fossil 

 remains of the Oolitic period. 



The development of the colours and shapes of our 

 modern dominant flowering plants under the influence of 

 insects was a later step, in tracing which the fossilised 

 remains of plants and animals give us only the negative 

 indication that there were neither such flowers nor such 

 insects until the chalk period that landmark of geologic 

 progress which in many ways marks off the more modern 

 animals and plants of the Tertiary perio^ from the Secon- 

 dary, in which great reptiles and the ancient cycads and 





