8 BULLETIN 53, HAWAII EXPERIMENT STATION 



Table 1 gives the annual number of fronds set per tree during four 

 successive years : 



Table 1. — Annual number of fronds set per tree (Cibotium chamissoi) during 



four successive years 



Tree No. 



Elevation, 3,500 feet 



Average . 



Number of new fronds de- 

 veloped 



1920 



1921 



1922 1923 



Aver- 



4. 67 

 6. 33 



5. 67 



6. 33 

 5 



5. 25 



5. 52 



Tree No. 



Elevation, 2,200 feet 



Average. 



Number of new fronds de- 

 veloped 



1920 1921 



1922 1923 



Aver- 

 age 



5. 25 

 5.5 

 5. 25 



4. 75 

 5.5 



5. 75 

 4.5 

 5.5 



25 



While the data given in Table 1 do not conform to the theory that 

 each of the five spirals is represented annually by a frond, they do 

 verify the observation that the average annual number is a fraction 

 over five, and show that this number is practically the same regardless 

 of altitude. 



It would seem, therefore, that the rate of growth of the tree fern 

 could be closely determined simply by measuring the vertical dis- 

 tance between any two successive frond pits of the same spiral and 

 by multiplying this distance by 5.39 and dividing by the spiral num- 

 ber, that is by 3, 5, or 8. For example, if this distance on the 5 

 spiral averaged 4 inches, the yearly vertical growth would be 

 5 39 



4 X — , or 4.31 inches; or, if measured on the 3 spiral, it was 2.4 



5 39 



inches, the yearly vertical growth would be 2.4 X — , or 4.31 inches. 



o 



In order to ascertain the average vertical distance between the 

 frond pits, eight trees {Cibotium chamissoi), growing near the Mill 

 plat, were stripped of their bark and measurements were made of 

 their diameter, length, weight, and the like. These data, together 

 with the rate of growth as computed by the foregoing method, are 

 given in Table 2 : 



