THE SPORE-PRODUCING MEMBERS 



695 



that the spore-producing members, whether sporangia or sporangiophores, 

 have been susceptible of considerable differences of position in the radial 

 plane, and that in this the sporangia show a parallelism with the sporangio- 

 phores which it is important to recognise in parts which are identical in 

 their function. 



The position of the leaves relatively to the spore-producing members 

 in strobiloid forms is usually, but not constantly, a subtending one : there 

 is reason to believe that a constant relation was a usual condition in 

 primitive forms, while the exceptions may be held to be secondary in their 

 origin. In the Lycopodiales the subtending relation of leaf to sporangium is 



FIG. 361. 



Diagrams illustrating the relation of spore-producing members and sporophylls or 

 bracts, and the results of their respective fissions, as seen in surface view from the 

 adaxial side. A=Lycopodium. B = Isoetes. C ~ Lepidostrobus. The dots in B and C 

 show the trabeculae. D^Tmesjfiteris. E = Psilotum. P'=Palaeostachya. G = Calamo- 

 stachys Binneyana. H=Calamostachys germanica. I = Sphenophylhwt ntaj'us. 

 J=Sphenopliyllnin Daivsoni. K=Cheirostrobus. L = Ophioglossum. M= abnormal 

 case of Ophioglossum (see Fig. 359 j, K). N^Helminthostachys. 



constant (Fig. 361 A, B, c), as it is also in those of Sphenophyllales wherever 

 there is a single sporangiophore to each bract-leaf (Fig. 361 D, E. i), but 

 it is departed from in those cases where more than one is associated 

 with each bract (S. Dawsoni, Romeri, p. 402, Fig. 361 j). The con- 

 dition seen in Cheirostrobus strongly suggests chorisis of both bract and 

 sporangiophore (Fig. 361 K), and their mode of insertion upon the bract- 

 whorl in other species of Sphenophyllum above quoted indicates it as 

 probable that some similar chorisis of the sporangiophores has been 

 effective in them also (Fig. 361 j). In the Equisetales the relation is 

 generally less exact : it seems still uncertain whether or not the sporangio- 

 phores were actually subtended by the bracts in Palaeostachya (Fig. 

 361 F): 1 in C alamo stachys they may be somewhat irregularly subtended by 



a See Hickling, I.e., pp. 372, 377. 



