110 THE EVOLUTION OF PLANTS 



shown by its structure. In other species, however, 

 similar seeds have been found on the naked 

 branches of a frond-like organ, so it seems that 

 the seeds were produced on a part of the frond 

 which did not have any leaflets (fig. 12, a). There 

 was thus a certain difference between the sterile 

 and fertile parts of the leaf, such as we find 

 in the Royal Fern (Osmundd) and many other 

 Ferns at the present day. 



The discovery of these highly organised seeds 

 showed at once that Lyginodendron was far re- 

 moved from the true Cryptogamic Ferns, and 

 was indeed already a Seed-plant, allied to the 

 Cycadophyta. 



But still our knowledge of the plant was in- 

 complete, for nothing certain was known of the 

 male organs. The pollen-grains had been seen 

 in the pollen-chamber of the seed, but where had 

 they come from? Mr. Kidston solved this prob- 

 lem in 1905, when he found the pollen-bearing 

 organs hi connection with the foliage of Lygino- 

 dendron. The polliniferous part of the frond 

 bears, instead of the ordinary leaflets, little oval 

 discs, two or three millimetres in length (see 

 fig. 12, 6); on the under side of each disc there 

 are six or seven two-chambered pollen-sacs of a 

 spindle shape. This type of fructification was 

 known long before its connection with Lygino- 

 dendron was established, and as it occurs in a 



