12 



Göte Turesson 



are all horizontally expanded and firmly pressed to the ground, suppressing under 

 their flat rosettes most of the surrounding plants. This species behaves, therefore, 

 in the same way as Hypocliœris radicata and Leontodon autumnalis, described and 

 figured by Wakming (31). Lindman adds that the basal leaves of Hypochceris are 

 not able to do any harm in shady places where grass and laller plants are growing, 

 as they are then forced into an upright position. A still more striking example 

 of a plant suppressing accompanying plants by virtue of its horizontally expanded 

 leaves is cited by Lindman from northern England, namely Juncus Squarrosus 

 No information is given by Lindman as to the cause of the peculiar mode of growth 

 in Juncus. It should be added, however, that the same mode of growth may be 

 observed in other places where this species grows abundantly, for instance, on the 

 west side of Hallands Väderö. 



There are undoubtedly additional references in the literature to shore plants 

 and other plants exhibiting prostrate growth. However, the reports already dis- 

 cussed suffice to give an idea of the frequent occurrence of such growth -forms 

 They are found almost everywhere, and most of us have noticed the fact. A few 

 additional data relating to the North American flora may be cited. In some places 

 in the West, for instance in the vicinity of Seattle, Washington, the introduced 

 Hypochceris radicata is a pestilent weed in short-cut lawns, behaving here in the 

 same way as in England, as reported by Lindman. As regards littoral plants I 

 have found several prostrate ones on the west coast of North America belonging to 

 difïerent genera {Atriplex, Lathyrus etc.) On lake shores one often finds Roripa 

 curvisiliqua, different species of Veronica etc. wholly prostrate. Hypericum canadense, 

 HosacTcia deciimbens, and species of Phlox are also good examples of North American 

 plants which when growing in exposed localities bend downwards and become pressed 

 against the soil. 



While staying at the Plant Ecology Station on Hallands Väderö during last 

 summer, an excellent opportunity was offered to study the physiological nature 

 and the cause of the plagiotropic mode of growth in shore plants. The experience 

 gained from cultural experiments with different species of the genus Atriplex, per- 

 formed for some years in ray garden in Malmö, became of great service in these 

 studies. The following forms (raised from seeds) of the genus Atriplex were in- 

 vestigated: A. Bahingtonii; A. hastatum; two pure races of A. picitulum, one erect, 

 in the following called A. pat. ereclum, and one prostrate, in the following called 

 A. pat. prostratum ; two pure races of A. latifolium, one erect called Ä. laf. erectum, 

 and one prostrate, called A. lat. prostratum ; A. prostratum, Bough., a creeping small- 

 leafed very characteristic species growing on sandy beaches, formerly often called 

 A. depressa Hn. (Bot. Not. 1846). Some additional plants were also investigated, 

 including Glyceria maritima, Leontodon autumnalis, Roripa palustris, Plantago eorono- 

 pus, Sueda maritima, Cotoneaster integerriina, and Prunus spinosa. It was soon found 

 that Atriplex prostratum Bough, was by far the most suitable plant and, conse- 

 quently, this species was used in most of the experiments. 



