140 



ANCIENT PLANTS 



large sausage-shaped sporangia were attached (see fig. 

 98). The tips of the sporophylls overlapped and afforded 

 protection to the sporangia. The axis of the cone had 

 a central stele with wood elements like those in the 

 stem. The appearance of a transverse section of an 

 actual cone is shown in fig. 99. Here the sporangia 

 are irregular in shape, owing to their contraction after 



ripeness and during 

 fossilization. Other 

 cones had sporangia 

 similar in size and 

 shape, but which pro- 

 duced spores of two 

 kinds, large ones re- 

 sulting from the ripen- 

 ing of only two or 

 three tetrads in the 

 lower sporangia, and 

 numerous small ones 

 in the sporangia 

 above. 



The similarity be- 

 tween the Lepidoden- 

 dron and the modern 

 Lycopod cone has 

 been pointed out al- 

 ready (p. 67), and it 

 is this which forms the principal guarantee that they 

 belong to. the same family, though the size and wood 

 development of the palaeozoic and the modern plants 

 differ so greatly. 



The large group of the Lepidodendra included 

 some members whose fructifications had advanced so 

 far beyond the simple sporangial cones described above 

 as to approach very closely to seeds in their construction. 

 This type was described on p. 75, fig. 54, in a series of 

 female fructifications, so that its essential structure need 

 not be recapitulated. 



Fig. 58. — Longitudinal Diagram, showing the 

 arrangement of the elongated sporangia on the 

 sporophylls 



a, Main axis, round which the sporophylls are in- 

 serted; s, sporangium; j, leaflike end of sporophyll. 



