HAWAIIAN TEEE FERN AS A SOURCE OF STARCH 



7 



bottom to top if there were an appreciable growth within the 

 trunk. 



Many species of monocotyledonous trees show an increase of 

 growth at the base of the trunk, as is frequently evidenced by the 

 dead roots which are found covering 2 or 3 feet of the base of the 

 tree trunk. That this is not the case with the tree fern is shown 

 by the uniform occurrence of pits from which the fronds once pro- 

 truded along the entire length of the trunk. It would seem, there- 

 fore, that such growth in the tree-fern trunk is negligible. 



The method of growth at the top of the trunk, however, is very 

 striking. In the early spring new fronds or leaves develop, a com- 

 plete circle of new fronds averaging five in number emerging from 

 the heart of the crown at practically the same stage of development 

 (PI. IV, fig. 1). These fronds attain full size within about three 

 months after the time of their appearance and remain on the tree 

 from 18 to 24 months: An occasional immature frond can be found 

 on the tree after the first five fronds develop. 



METHOD OF DETERMINING THE RATE OF GROWTH 



When the outer bark is stripped from the tree fern, or when an old 

 log in which the starch core has decayed is split open, the fronds are 

 observed to be arranged in definite spirals. Figure 1 represents 

 graphically the surface of a tree-fern log from which the outer bark 

 has been removed to disclose the location of the frond attachments, 

 regarded as a hollow cylinder cut lengthwise and laid out flat. The 

 ellipses represent frond pits or the openings in the bark from which 

 the fronds protruded. 



A number of different spirals are apparent in the diagram. Among 

 the more obvious are those parallel to the lines o-d\ n-d', and m-a\ 

 respectively. 



The arrangement of fronds was found to be the same on a large 

 number of stripped tree-fern logs, and the spiral combination of 3, 5, 

 and 8 fronds could readily be counted. The only difference noted 

 was in the direction of growth of each spiral, which was clockwise 

 on some trees and counterclockwise on others. 



Since probably a circle averaging five fronds is developed each 

 spring, each of the five spirals would seem to be annually represented 

 by one frond. If this were true, or if the average yearly number of 

 fronds per tree showed little variation in the different trees, it would 

 be necessary only to measure the vertical distance between two frond 

 pits on one of the five spirals to determine the annual growth of the 

 tree (PI. IV, fig. 2). 



To determine the correctness of this assumption, the fronds of a 

 number of trees growing at different altitudes were marked with 

 copper tags at each frond-setting period and the trees were visited 

 once a year. Usually, it was not difficult to distinguish the new 

 fronds. The species Hapu (Cibotium chamissoi) , which is the only 

 one used to any extent for starch production, was selected for this 

 study. 



