This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Hog plants as a whole are strikingly homogeneous in their habit of growth. The dominant habit is the grass habit, as in the case of the Sedges, Cotton Grass, etc. But the rosette habit is also not uncommon, as in Butterwort, Grass of Parnassus, etc. The trailing habit is met with in the case of the Hog Pimpernel, common also to the marsh flora. The shrub habit is found in the case of Cranberry, Wild Rosemary, and Bog Myrtle. In all cases there is a marked reduction in leaf and stem owing to the xerophytic adaptations which the bog plants have acquired.
The marsh flora is more or less similar in general characteristics to the bog flora, as far as the dominance of the grass type is concerned, but contains numerous other types less usual in the bog flora.
Some plants are procumbent types, such as the Bog Bean. Non-glumaceous plants adopt the grass habit when associated with Grasses, e.g. Bog Speedwell, Bog Asphodel, and Great and Lesser Spearworts. The inversely pyramidal habit is found in Marsh Marigold and Marsh Lousewort.