SPORE-PRODUCING MEMBERS 



It remains now to consider the > morphological character of the sporangio- 

 phore in the Equisetales. The current view of the strobilus of Equisdum 

 is that it is a product of meta- 

 morphosis of the sterile shoot, 

 and that the sporangiophore 

 is an altered sterile leaf. This 

 has been re-stated lately by 

 Goebel, 1 on the basis of de- 

 velopment of the individual, 

 but without bringing the fossil 

 Calamarian strobili into the 

 comparison. It may, however, 

 be safely asserted that if Equise- 

 tum and Ec/uisetites had never 

 existed, a comparison of the 

 Calamarian strobili with those 

 of other Pteridophytes would 

 have led to a different view ; 

 it will be necessary therefore 

 to examine this natural group 

 of the Equisetales as a whole, 

 and not only one isolated genus, 

 even though that type be the 

 well-known one now living. 



Taking first the developmental evidence derived from Equisetum, as 



FIG. 209. 



Equisetum limosum, L. Median longitudinal section of a 

 sporangium at the base of the strobilus, together with the 

 annulus (a), x 200. 



FIG. 210. 



Calatnostackys Caskeana. Tangential section, showing four sporangia grouped around 

 their sporangiophore (s/>). Three contain megaspores and one microspores. X30. Phil. 

 Trans. II'. and S. Will. Coll., 1587. (From Scott, Studies in Fossil Botany:) 



;iven by Goebel, 2 it is found that, notwithstanding the difference in mature 

 form (which Goebel notes, and from which he concludes that the distinction 



1 Organography, vol. ii., pp. 499-503. 2 Z..c., p. 500. 



