A COMPARATIVE STUDY OF GEUM RIVALE L. AND G. URBANUM L. TO DETERMINE THOSE FACTORS CONTROLLING THEIR ALTITUDINAL DISTRIBUTION: I. GROWTH IN CONTROLLED AND NATURAL ENVIRONMENTS.

The comparative growth of Geum rivale L. and Geum urbanum L. was determined, both over a range of temperatures under controlled conditions and throughout the year in field plots at three altitudes in the northern Pennines. Although under controlled conditions, the total dry matter accumulated was similar in both species, the change of relative growth rate with time was much more pronounced in G. urbanum than in G, rivale, especially at lower temperatures. In the field situation, there were no consistent differences in the overall growth pattern of the two species. The effect of altitude on growth was most pronounced during autumn and winter but was minimal in the summer. Root growth was less temperature-sensitive than shoot growth in both species and was enhanced during the autumn. It is concluded that climatic limitation of growth is not so severe as to be the sole factor determining the altitudinal distribution of the species pair.