Ma)ic]iester Memoirs, Vol. Ivi. ( 1 9 1 2), No. .11. 15 



branches. This phenomenon appears to be confined to 

 those instances in which the branches are crowded together 

 at one level, i.e., in those included in the subgenus Cala- 

 mitina. I have met with no examples, figured or in speci- 

 mens, amongst the Encalamites or the Stylo-calamites. 



{b) That each period or cycle showed, immediately 

 above the node at which the branches arose, one or more 

 very stunted internodes, and immediately beloiv it a 

 comparatively long internode, which might either be the 

 longest, or second to the longest in the whole series. 



Significance of Cycle. Mr. Horwood's opinion that 

 the approximation of the diaphragms strengthens the 

 stem against the strain of superposed branches cannot be 

 considered as upheld by a fact which he apparently 

 infers in his paper — that the branches spring from the 

 node immediately above the short internode. 



I would suggest that the mode of growth under 

 discussion was not a purposive arrangement at all. It 

 might, with greater likelihood, be a consequence arising 

 from the disturbance of normal physiological conditions 

 at a level where important morphological changes took 

 place. It may very possibly have happened that the 

 diversion of a great amount of food material outwards 

 to the secondary members impoverished the supply avail- 

 able for the normal increase in the primary axis, and 

 retarded growth in the neighbourhood of the branch 

 whorl. The group of shortened internodes would have 

 to be considered as a result of, rather than as a prepara- 

 tion for, the appearance of the branch system. 



This explanation is what I regard as the best. It is 

 quite consistent with the fact that the phenomenon is to 

 be found only in those Calamites in which the branches 

 are closely crowded at certain levels, and in which the 

 disturbance of uniform growth is at its maximum. 



