PAST HISTORIES OF PLANT FAMILIES 151 



respects slightly more complex. Round each cone axis 

 developed rings of sporophylls which alternated with 

 sterile sheathing bracts. Each sporophyll was shaped 

 like a small umbrella with four spokes, and stood at 

 right angles to the axis, bearing a sporangium at each 



Fig. no. Longitudinal Section of Part of Calamites Cone 



br, Sterile bracts attached to axis ; sp, attachment of sporophylls ; s, sporangia. 

 At x a group of four sporangia is seen round the sporophyll, which is seen at a. 

 (Microphoto.) 



of the spokes. A diagram of this arrangement is seen in 

 fig. 109. 



A photograph of an actual section of such a cone, 

 cut slightly obliquely through the length of the axis, 

 is seen in fig. 1 10, where the upper groups of sporan- 

 gia are cut tangentially, and show their grouping round 

 the sporophyll to which they are attached. 



A few single tetrads of spores are enlarged in fig. 

 in, where it will be seen that the large spores are of 

 a similar size, but that the small ones of the tetrads 



