Sargent, Charles S. 1889. Vaccinium hirsutum. Gard. & Forest. 2: 364, 365, fig. 119.
Ericaceae
Species Description - Plants usually in small and compact colonies, 15-40 cm. high. (The twigs of the current season green.) Leaves deciduous, deep green; the lower surface shining and non-glandular, glabrous or sometimes pubescent along the veins; broadly elliptic, 1-1.5 cm. wide, 1.5-3 cm. long; the margin serrate. Corolla broadly cylindraceous, 4-8 mm. long, usually white. Fruit bright blue, 8-12 mm. in diam., of excellent flavor.
V. pennsylvanicum Lam. Eneye. 1: 74. 1783. Not V. pennsylvanicuwr Mill. Gard. Diet. ed. 8. 1768.
Tetraploid (2n = 48).
V. lamarckii is the autotetraploid derivative of V. angustifoliurn. As in other instanees of this type, there might be some convenience in considering them as subspecies of a euploidion; however, where growing together they are so dif- ferent that there seems to be little possibility of confusing them (fig. 8). The recognition of "var. angustifolium" is evidence that various students for many years admitted the presence of twpo separable entities, and since we now know that they are genetically disjuet there seems to be little reason for not recognizing them as two species.
Although often growing together, it is likely that future work will reveal that the basic ecological requirements of V. angustifolium and V. lamarckii differ; certainly their responses to the same environmental conditions at times are quite unlike. As noted above, V. lamarckii is more sensitive to fire; in fact, repeated burning appears to be the factor which permits V. angu,stifoliu,m to produce the vast blueberry fields of Maine, etc. Under those conditions it is usually able to compete with all but a few of the native and introduced plants (see Mason & Chandler 1945). Under the same conditions, the basal buds of V. lamarckii apparently are seriously injured or killed, so that the plants gradually dwindle and eventually are eliminated.31 Also, although we have no actual comparative measurements made under controlled conditions, our observations of individuals whose planting dates were known would indicate that a plant of angustifolium spreads considerably faster than one of latmarckii, which would be a factor in competition'2 However, the greater height of lamarckii would permit it to live under conditions which would exclude angustifolium, as in competition with rank-growing Gramineae and Cyperaceae, or various genera of low-growing shrubs. Therefore, the coarser plants of this series sometimes found in swampy or boggy areas probably are not more robust merely because of the greater amount of available water and more fertile soil, but because they are the taller- growing tetraploid and able to compete under those conditions. On the other hand, the greater height of lamareckii acts to its disadvantage in open, wind- swept areas. There, the upper parts of the plant (which bear the buds for the next season's flowers and fruit) would be more likely to be above the snow and so either be winter-killed by desiccation, or be more easily found and eaten by brows- ing animals such as deer, moose, and caribou, thus holding the tetraploid popula- tion in check by controlling its reproduction. Observations at low and high elevations in Maine indicate that both factors are operative and they may be the principal reasons why lamarckii usually does not ascend so high on mountains, and seems not to penetrate so far north as angustifolirnm. A future careful sur- vey of the situation will probably indicate that the main populations of the two species tend to be ecologically disjunct, although individuals can and often do occur in the same habitat.
Hybrids are known in the Virginia mountains between V. lamarckii and both V. simulatum and V. alto-montanum; and V. lamarckii is the species which, with V. corymbosum, seems to have been most instrumental in producing the many perplexing halfhigh populations within the glaciated area. Since both tetraploid and diploid highbush plants are to be found together in many of these swampy areas, the preponderance of tetraploid hybrids over the diploids can probably be explained by the fact that the greater stature and better competitive ability of lamar5kii in swampy areas has permitted it to approach the zone of the highbush plants more closely than the lower-growing diploid V.- angustifotlium. However, in morainal areas, and where ecological disturbances have been accentuated by partial drainage, the lowbush diploid-s often penetrate to the hummocks in these areas and so make contact with the highbush diploids. Southward, in the Appa- lachian Mts., those phases of V. lamarckii which have pubescence along the veins apparently have acquired this aberrancy through gene-exchange with V. simu- latum; northward, superficially similar plants have gotten their pubescence through gene-exchange with the pubescent phases of V. corymbosum. Further reference to these hybrid and segregate plants will be found in tho discussion both in Section V of the key, and under V. corymbosum.
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