11 



date are also large here, so tliat the averages are very uueertain, but on Table II 

 tliev varv in a definite direction: they are liighest in summer, lowest in spring and 

 winter. From this we may conclude that the leaves are loijgest in tlie warm 

 summer time, July — September, wheu they are generalh' upwards of 150 cm. loug. 

 From September they decrease in lengtli, i. e. the lougest leaves are throwu off 

 and tlie new oues growu are not so loug; in winter they are ouly ea. 100 cm. 

 long. In spring they are also comparatively short, though the unusually low num- 

 bers from the 15th of May are accidental, and the longer leaves develop only in 

 June; lastly, in mid-summer (July — August) the leaves reach tlieir maximum 

 length. We may therefore say that the leaves of the Zostera vegetation 

 in deep water and on soft bottom are much longer in summer than in 

 winter and spring. Tlie Table further shows that with increasing length of the 

 leaves in summer follows their greater breadth. 



The Tables III and IV come from tlie same collections; they contain 

 measurements of the length of all the leaves of some piants, arrauged so that each 

 line corresponds to one specimen; the first number (to the left) gives the length 

 of the outermost leaf, the next that of the following leaf etc. to lastly, that of the 

 innermost leaf uot yet fuU grown. Each month 3 — 7 specimens were measured 

 and the number which marks tlie lougest leaf of each specimen is accentuated; a 

 dash iustead of number meaus that the leaf in questiou was defective on account 

 of the absence of the tip. 



Here both tables agree and show the same, though Table IV most clearly, 

 uamel}', that the outermost, i. e. the oldest leaf, is the longest throughout 

 the autumn and winter, whereas in mid-summer the second, the third, 

 l'ourth or eveu the fifth outermost leaf is the longest; this is in good 

 accordance with what we have learut from Table II. 



Table IV. 



Channel off Holckenhavn. 



Soft bottom, 2V — ok fatlioms. 



The length of all the leaves of some piants (in cm.); 



each line corresiionds to one plant. 



1901-02 



Outermost — innermost leaf. 



