818 Yapp. — Spiraea Ulmaria , L. } and its Bearing on the 
rhizome with its winter buds. The plant thus belongs to Raunkiaer’s class of 
‘ hemicryptophytes ’. l The winter buds begin to unfold during March, and 
each produces several radical leaves. In a vigorous adult plant such a bud 
may subsequently form an erect flowering shoot, with cauline leaves. In 
young plants, or buds of less vigour, however, the shoot does not elongate, 
but remains prostrate. In the latter case it continues to form radical 
leaves till September. These two kinds of shoot will be referred to in 
this paper as the erect flowering shoots and the non-flowering shoots 
respectively. 
Text-fig. i shows that Ulmaria is widely spread over the north tem- 
perate and colder regions of the Old World. In Great Britain it is a com- 
Text-fig. 2. Sympodial rhizome of Spiraea Ulmaria, showing four years’ growth. The winter 
bud has unfolded (April), but has not yet formed the erect flowering shoot. Leaves are numbered in 
order of age. About § natural size. 
mon plant, being found in the whole of Watsons 112 counties, 2 whilst 
its altitudinal range is from the coast to some 2,700 feet above sea-level. 3 
Itself a characteristic plant of the drier parts of marshes and fens, 4 the 
habitat of Spiraea Ulmaria is usually where the water content of the soil 
is considerable rather than excessive. It prefers soils with a high water 
capacity, such as peat or clay. Provided that its needs in respect to soil 
moisture are satisfied, it will grow almost anywhere : at the edges of marshes 
and rivers ; in the damper parts of meadows ; in roadside ditches ; on the 
sea-coast ; 6 in damp hollows between sand-dunes ; 6 and even in woods, if 
1 Raunkiaer (’07), p. 49 . 2 London Catalogue (’08). 
3 Watson (’47), p. 334 . 4 Yapp (’08, second paper), pp. 7° and 7 2 * 
5 In 1910 my friend Professor Weiss sent me some specimens collected close by the sea, growing 
practically in brackish water. 6 Moss (’07), p. 16 . 
