I. Introduction, 



At tlie reijuest of Dr. G. G. Joh. Peterseu, Director of tlie Dauisli Biolo- 

 gical Station, tlie autlior made a tliree weeks cruise in Danish waters within the 

 Skaw on board tlie Biologicai Station's steamer »Sallingsund« in July and August 

 1901, in order to investigate the distribution of the eel-grass or grass-wrack 

 and to study the eeology of this plant. As assistant at the Biological Station I had 

 already tlie year before taken much interest in the grass wrack, the extensive 

 growth and distribution of whicli is of much importance to our fislieries. The 

 following pages show the results of my investigatiuns. Unfortunately, I have been 

 so much occupied by other work that this report is only now completed six years 

 later; yet a very brief summary of the most important results has already been 

 published in the »Botanisk Tidsskrift« (Vol. 27, December 1905, pp. 123-125). 



The grass- AV rack [Zostera marina L.) being such a common and peculiar 

 plant, it is only uatural that many investigations of various kinds should have 

 been published regarding it. The object of my investigations has therefore mostly 

 been to exteud our knowledge of the conditions of the growth and occurreuce of 

 this plant in the Danish seas and less to stud}' tlie structure, life or biology of 

 the plant itself. In the first and third reports of the Biological Station (1891 and 

 1893), Dr. G. G. Joh. Petersen has already recorded sirailar investigations, made 

 in Holbæk Fjord and the Little Belt; f urther information on the distribution of 

 the eel-graSs in the Kattegat is to be found in: »Det videnskabelige Udbytte 

 af Kanoubaaden Hauchs Togter« (København 1893, pp. 437 — 438). In 

 all three publicatious the text is accompanied by several charts showing the distri- 

 bution. Information on this subject may also be gathered from later reports of 

 the Biological Station (especially Reports IX and X, 1900 and 1901). With regard 

 to our Baltic shores, lastly, it may be mentioned that in his paper on the -Algen- 

 flora der westlichen Ostsee deutschen Antheils« (6. Bericht der Komm. zur 

 wissensch. Unters. der deutschen Meere in Kiel, 1889) Prof. J. Reinke of Kiel 

 has discussed the eel-grass vegetation ofl the Schleswig side of tlie Little Belt and 

 in Iviel Bay. 



A work of great importance but of a somewhat ditferent kind is the »Dansk 

 Plantevækst, I, Strandvegetation« lately (1906) published by Prof. Eug. 



