Manchester Meinoiys, Vol. Iv. {\gi\), No. 0. ii 



that is, that there is one strand passing between each pair 

 of sporangia throughout {Text-Jig. V. 4). 



The spiral arrangement may therefore, quite reason- 

 ably, be regarded as a secondary modification, admitting 

 of the insertion of an unusually large number of sporangia, 

 and probably correlated with the crowded arrangement of 

 the parts. 



One last point in support of this view is that, though 

 the number of vascular bundles throughout is considerably 

 in excess of the normal, this is to be regarded as a 

 necessary concomitant of the extra demands placed upon 

 it, the characteristic, dominant, central strand being readily 

 distinguishable from base to apex and terminating the 

 main fertile spike. 



Summary. 



1. The specimen represents a condition of the fertile 



Ophioglossaceous spike derived by a process of 

 splitting or chorisis. 



2. Its robust character makes great demands upon 



the vascular supply and this is increased pro- 

 portionately. 



3. The view that the specimen has arisen by chorisis 



and does not represent two fused axes is supported 

 by the following anatomical features : — 



i. There is a single dominant median strand 

 throughout. 



ii. The sporangial vascular supply is normal. 



iii. The vascular supply to the accessory spikes 

 is in close agreement with that figured by 

 Bower for Ophioglossuni palmatum and 



