Mutations and Evolution. 
185 
The ordinary poison ivy, Rhus toxicodendron of North America, 
has fruits glabrous or nearly so. A. H. Moore, 1 records from 
Bristol, Maine, a form malacotrichocarpum with fruits abundantly 
pilose. Oxalis stricta, var, viridiflora was described by Hus from 
St. Louis, 2 differing from the type in having green petals. The 
same form was afterwards found in plenty by Bartlett 3 near 
Thomson, Georgia, doubtless arising from an independent mutation. 
The petals are broader, apparently owing to a change in the shape 
of the cells, and the presence of chloroplasts may perhaps represent 
an independent change. Melica (Avena) stricta Michx, has glumes 
strongly tinged with purple. Forma albicans Fernald, 4 the 
prevailing form on some of the mountains of Maine and Eastern 
Quebec, has glumes whitish or pale straw-coloured. Drosera 
rotundifolia var. comosa is a dwarf variety found by Fernald 5 in a 
bog at the mouth of the Grand River, Gaspe Co., Quebec. It has 
a sub-capitate inflorescence of few flowers, petals coloured, and the 
ovary tending to develop into a rosette of grandular leaves. This 
dwarf occupied a considerable area in abundance almost to the 
exclusion of the normal. It is evidently a mutational form able to 
survive in favourable conditions. 
Gaylussacia resinosa, the common huckleberry of America, has 
black berries without a bloom. Var. glaucocarpa Robinson is 
common in Eastern Connecticut 6 where it occurs in distinct clumps 
generally associated with the species, from which it differs in 
having blue glaucous fruits and also in its greater vigor and glaucous 
leaves. Fernald (1917) describes a colony of Bidens by Lake 
Pocotopaug, Connecticut, which differs from the species B. connata 
of that region in having flat 2-awned achenes like B. heterodoxa of 
Prince Edward Island. He interpretes it as an outlying colony of 
the northern species, but since its leaves resemble B. connata and 
its var. petiolata it more probably represents a parallel mutation. 
The American saxifrage, Tiarella cordifolia L., extends from 
New England to Minnesota and southwards. In Maine, New 
Hampshire and Vermont two forms are found. 7 The plants differ 
1 Rhodora, 11 : 162. 1909. 
a Rept. Mo. Bot. Garden, 18 : 99, 1907. 
» Rhodora, 11 : 118, 1909. 
4 Rhodora, 7 ; 244, 1905. 
6 Rhodora, 7 : 8, 1905. 
6 Sheldon, J. L., Rhodora, 4 ; 14, 1902. 
7 Danforth, C. H., 1911. A dimorphism in Tiarella cordifolia. Rhodora, 
13: 192-3. 
