BULLETIN 53, HAWAII EXPERIMENT STATION 



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-Graph showing the spiral arrangement 

 of tree-fern fronds. 



The lateral growth of the 

 starch core would seem to be 

 negligible since it is immedi- 

 ately surrounded by a very 

 hard, brittle covering meas- 

 uring one-fourth to one-half 

 inchjin thickness, and appar- 

 ently is incapable of further 

 growth or expansion. In five 

 out of eight trees the starch 

 core was found to be appre- 

 ciably larger at the top than 

 at the bottom of the trunk, 

 which shows that as the tree 

 fern grows from a small lat- 

 eral shoot or spore to a large 

 size, the core grows corre- 

 spondingly larger at the top 

 only; and that the part first 

 formed does not increase in 

 diameter. Many trees are 

 found in which the starch 

 core tapers almost to a poiat 

 at the base. Trees grown 

 from very large lateral shoots 

 show little tapering of the 

 core, and trees resulting from 

 the turned-up crown of a 

 large fallen tree show none 

 at all. It is true that the 

 gross diameter of the tree, 

 especially of the species Cibo- 

 tium menziesii, increases with 

 the growth of the tree, but 

 this increase is due entirely 

 to the increase in abundance 

 of the air-feeding roots mak- 

 ing up the outer bark of the 

 tree. 



That there is no vertical 

 growth within the trunk,, 

 except at its apex, is shown 

 by the fact that the vertical 

 distance between frond pits 

 on the same spiral is the 

 same regardless of whether 

 the measurements are made 

 at the bottom or at the 

 top of the trunk. This 

 vertical distance would show 

 a gradual decrease from 



