also a distinct effect upon the structure of plants. Thus in the Mediterranean regions Ranunculus ficaria, as compared with the typical species growing in England, "bears finer and larger flowers and leaves, so that it is generally recognised as the variety Calthæfolia." Caltha palustris "has itself no recorded variety in low-lying situations." "When, however, this plant manages to get away from its habitual environment, and to reach 'mountainous places' (Hooker), it puts on characters which descriptive botanists have independently noticed and variously named as varietal or specific. It is commonly known as Caltha minor." "Many experiments have shown that if plants, or their seeds, be taken from lowlands and planted on alpine regions, all those that change their structures at once begin to assume more or less the same anatomical and morphological characters as the plants normally growing in highland regions."[1] Again, according to Kerner, a plant of the grass Glyceria fluitans "growing on damp soil on the edge of a stream over the water had linear bluntly-pointed leaves, whose sheaths were on the average 15 cm. long, the blades 23 cm. long and 8·5 mm. broad. After this plant had been submerged under rapidly-flowing water in the following year, leaves unfolded, which tapered gradually to a point, with a sheath having a mean length of 47 cm., and blades 73 cm. long, but only 5 mm. broad. The blades produced in running water were three times as long, and actually rather narrower than in the air."[2] According to Varigny, "Curtiss had seen in some places near the Potomac Bidens cernua acquire a height which is six times the common average height of this plant, and he has seen the same in Oxalis stricta; C. Lemaire states in D'Orbigny's 'Dictionary' that, while cultivated hemp grows no higher than a metre and a half in France, in Piedmont it attains three and four metres; and if Italian stock is planted in France it rapidly reverts to the small variety in the course of two or three years." "It is also well known that where mountain plants are transferred to the valleys and plains they lose the hairy covering which they generally possess, while valley plants transferred to the mountains acquire this same covering." "The common Dandelion (Taraxacum dens leonis) has in dry soil leaves which are much more
