X] ' PALAEOSTACHYA. 357 



aborted sister-cells like those noticed in C. Binneyana; this 

 phenomenon is well illustrated by the unequally nourished 

 spores in the sporangium of fig. 96, but no such starved spores 

 have been found in the microsporangia. In this cone, then, 

 heterospory has become firmly established, but the occurrence 

 of undersized spores in a macrospore-tetrad leads us back to 

 the probable lines of development of heterospory, which are 

 seen in G. Bimieyana at their starting-point. 



In the two species of strobili which have been described, 

 Calamostachys Binneyana and C. Casheana, the sporangiophores 

 or sporophylls are given off at right angles to the axis, and 

 midway between the sterile whorls. These are two of the 

 most important distinguishing features of the Calamitean cones 

 included under the generic term Calamostachys. In another 

 form of cone, which also belongs to Calamitean stems, the 

 sporangiophores arise in the axil of the sterile leaves, and are 

 inclined obliquely to the axis of the cone. To this type the 

 generic name Palaeostachya has been applied by the late 

 Prof. Weiss^ of Berlin. The portion of a cone shown in fig. 97 

 shows the arrangement of the sterile and fertile appendages 

 characteristic of Palaeostachya. 



Fig. 97. Palaeostachya pedunculata Will. Part of a cone, x 3. (After Weiss.) 



It is practically impossible to distinguish between cones 

 of the Calamostachys and Palaeostachya type* in the case of 

 imperfectly preserved impressions ; indeed we cannot assume 

 that all long and narrow cones with spirally disposed ver- 

 ticillate bracts are Calamitean. We must have the additional 

 1 WeisB (76), p. 108. 



