Pennsylvania. While it is true that these peculiar limestone outcrops maintain a characteristic flora, it is doubtful if there are any species of plants endemic upon them. The limestone thus appears rather as maintaining an aggregate of characteristic species than as definitely controlling the distribution or evolutionary history of any particular species. I think there is no species in our area that has been collected only on limestone, but many that seem to predominate there, notably some Crataegus, Amelanchier, sedges, Camptosorus, Asplenium, and a few others.7. The glaciated part of our range contains many ponds, swamps, and bogs and it is the latter that are of chief interest to the botanist.These undrained areas, usually, though not always, deficient in lime, and exhibiting a high degree of acidity, maintain a flora quite characteristic. It has been shown that that section of our area which was neither glaciated nor on the coastal plain does not contain the plants characteristic of the glacial bogs of the north and also found in the typical cranberry bogs of the coastal plain. It is certainly true that bogs are unknown in this region (see map, pi. 2), and that it contains no lakes or ponds of any size. It is significant that the following plants are found in the bogs of the coastal plain, mainly in the pinebarrens, and also north of the moraine, but unknown in the intervening unglaciated Piedmont Plateau in New Jersey; in Pennsylvania further study is necessary on this point. Chamaecyparis thyoides (see pi. 6), Blephariglottis cristata, Panicum linearifolkiin, Blephariglottis blephariglottis, Carex trisperma, Arethusa bulbosa, Carex Collinsii, Sarracenia purpurea, Xyris Congdoni, Drosera intermedia, Helonias bullata, Oxycoccus macrocarpus, Gyrotheca tinctoria, Aster spectabilis.