•6o ANCIENT PLANTS 



microscopic structure of the two roots when cut in trans- 

 verse direction. The various tissues will be recognized 

 as coming into the table on p. 54, so that both in the 

 details of individual cells and in the general arrangement 

 ■of the cell groups or tissues the roots of these fossil and 

 living ferns agree. 



Among stems there has been at all periods more 

 variety than among the roots of the corresponding plants, 

 and in the following chapter, when the differences be- 

 tween living and fossil plants will be considered, there 



Fig. 35. — A, Root of Living Fern. B, Root of Palaeozoic Fossil Fern, c. Cortex; fx, 

 protoxylem in two groups ; m, metaxylem ; s, space in fossil due to decay of soft cells. 



will be several important structures to notice. Never- 

 theless, there are very many characters in which the 

 stems from such widely different epochs agree. The 

 plants in the palaeozoic forests were of many kinds, and 

 among them were those with weak trailing stems which 

 climbed over and supported themselves on other plants, 

 and also tall, sturdy shafts of woody trees, many of which 

 were covered with a corky bark. Leaves were attached 

 to the stems, either directly, as in the case of some living 

 plants, or by leaf stalks. In external appearance and in 

 general function the stems then were as stems are now. 

 In the details of the individual cells also the likeness is 

 complete; it is in the grouping of the cells, the anatomy 

 of the tissues, that the important differences lie. It has 



