13 



The essential points are best seen in Table IV: in September and October the 

 long summer leaves are tlie outermost leaves; in November the outermost and 

 longest leaf is considerably shorter; at this time the summer leaves have been 

 tiirown off. This is the state of the plant till in the month of April; but in May 

 it begins to be altered, as can be seen nicely and regularly in June especially, 

 when in all 7 piants mcasured the fifth leaf is the longest; then tlie longest leaf 

 moves further out, yet even in August it is the second or third outermost and 

 not until September is it the very outermost. 



The question is now, whether by means of these tables it is possible to 

 draw a eonclusion as to the number of leaves produced by the grass-wrack in the 

 course of a year, and in this respect the answer is not very favourable. It must 

 be remenibered that only the outer leaves are fullgrown, as is most clearly seen 

 when measured, only these having long sheaths. The faet is that the sheath is 

 the part of the leaf which is latest in completing is growth. Taking e. g. the 

 o specimens whose lengths of leaves have been entered on February 15th 1902, we 

 have the following measurements: 



Length of leaves with sheaths. Leiigth of oorrespomling sheaths. 



130 118 100 65 38 15 30 28 20 13 O') O 



93 80 50 30 8 20 15 8 O O 



85 78 55 38 5 20 15 10 O O 



63 65 60 58 48 23 18 18 18 13 3 O 



73 65 55 45 28 10 19 15 12 7 O O 

 Similarly also on June 15th 1902: 



Length of leaves with sheaths. Length of oorresponding she.aths. 



76 71 85 93 104 90 52 21 22 20 25 25 3 O 



— 53 64 79 86 77 40 — 16 19 22 18 1 O 



— 97 127 160 170 145 90 25 29 33 44 25 2 O 



To judge from the length of the sheath in the first example, scarcely more 

 thau 2 — 3 leaves have fiuished their growth in length, in the last example 4 or 

 perhaps 5 have. On this is founded the opinion above stated, that each shoot has 

 at a certain time only 3 — 6, most often 4 — 5, fuU-grown leaves. 



As it is thus impossible to make sure that the leaves on the iuner side of 

 the longest leaf are full-grown, one cannot draw any eonclusion as to their length 

 being final. I do not think therefore that by means of the tables it is possible to 

 decide the exact yearly number of leaves on one shoot. Taking for granted that 

 the growth during the wiuter half-year (November — April) is extremely small, I 

 venture however to express the supposition that the grass-wrack yearly 

 produces 4 to 6 new leaves on each shoot. It is seen that the place of the 

 lougest leaf on the table chauges according to the time of the 3'ear and it seems 

 to me that this faet lends some countenauce to the supposition. The production 

 of leaves is of course rather variable according to the nature of the place, for 

 under favourable conditions the growth is more considerable and possibly more 

 leaves are developed than under bad conditions. 



The place near Nyborg gives an example of the Zostera vegetation in fjords, 

 where we find the most perfect dcvelopmcut of tliis plant. From the following 



') The sheatli i.s yet i|nite nndeveloiieJ. 



