﻿Manchester Memoirs, Vol. xlix. (1905), No. 17. 5 



sented in fig. 1, the lateral branches from the main 

 stem did not come off quite horizontally but were directed 

 obliquely upwards. Thus the central cylinder of the 

 lateral branch, which is cut obliquely, is found in fig. 1, 

 below the horizontal crack which traverses the main 

 stem while on the outside of the stem it will be 

 seen as a little central projection well above the 

 horizontal fissure. The oblique upward direction of the 

 branch prevents the details of the structure from being 

 distinctly visible, but fig. 4, which is taken from a 

 transverse section of a similar stem from the Cash 

 Collection in the Manchester Museum (Cabinet number 

 Q 384) shows the details of structure very clearly. The 

 two axes are still organically connected, but while the left 

 hand stem has a considerable amount of secondary wood 

 the right hand branch has little or no such thickening. 

 At the same time, judging from the two axes, the branch- 

 ing seems to have been a little less unequal than in the 

 above specimen. 



A similar specimen to fig. 4 but showing branches 

 cut transversely on either side of the main axis, is in the 

 possession of Dr. D. H. Scott. Though it is very likely 

 that unequal branching, such as described above, is 

 generally accompanied by such a difference in the vascular 

 tissues, as is seen in these specimens, yet it is not certain 

 that this difference was always present. For Williamson 

 ('95)* mentions a case of " unequal dichotomy, but of the 

 type in which, though one of the two resultant branches 

 is very much smaller than the other, there is no difference 

 in the details of their organization." This dichotomy he 

 stated occurred in the largest section of the Selaginoides 

 type which he had yet discovered, so that one would infer 

 that both must have shown a very considerable amount of 



♦Williamson, ('95), p. 4. 



