596 



STRXJCTURE AND LIFE HISTORIES 



found in the English "coal balls"' has disclosed both the 

 microsporophylls, bearing pollen-sacs, and the megasporo- 

 phylls, bearing, not merely megasporangia, but true seeds. 

 The ovule h.a.s a. pollen-chamber, like the cycads, except that 

 it projects a bit through the micropyle, and, strange as it 

 may seem, fossil pollen-grains have been discovered, well 

 preserved within this chamber. The seeds, about }i inch 

 long, have been described as resembling little acorns, en- 



FiG. 418. — Restoration of a seed of Lyginodendron oldhamhim {Lagenos- 

 tema Lomaxi), from a modelby H. E. Smedley. (After Scott.) 



closed like hazelnuts in smaller glandular cupules (Fig. 

 418). They are similar to those of the cycads, except 

 that they are not known to have organized an embryo with 

 cotyledons and caulicle. Instead, the tissues of the 

 female gametophyte only are so far found, retained within 



'■ Coal balls are "concretions of the carbonates of lime and magnesia 

 which formed around certain masses of the peaty vegetation as centers 

 and, through inclosing and interpenetrating them, preserved them from 

 the peculiar processes of decay which converted the rest of the vegetation 

 into coal. In them the mineral matter slowly replaced the vegetable 

 matter, molecule by molecule, thus preserving the cellular structure to a 

 remarkable degree. Such balls are especially frequent in the coal of 

 certain parts of England (Lancashire and Yorkshire)." 



