In some respects the bog and marsh are difficult to study on a sys-tematic plan; for the peaty soil and wet conditions render both inaccessible for a large part of the year, and the vegetation is so close and tall, that anything like the detailed survey recommended for meadows, woods, the cornfield, coast, etc., is rendered difficult. But the frequent arrangement of the plants in wide associations is a feature which renders the survey less formidable than at first appears.

Attention ought to be paid especially to the soil, depth of peat, nature of the water, etc, and these conditions should be correlated with the adaptations of the plants to xeromorphic conditions. Otherwise surveys may be made as in the case of a meadow.

In the marsh the tree associations may be noted first, and then the scrub. The dominant types and larger associations should be mapped out on a broad basis.