Abstract
Leaves of blackbrush (Coleogyne ramosissima Torr.) shrubs share a number characteristics of leaves of both xerophytic and sclerophyllous shrubs. Despite some leaf surface (morphological) and anatomical similarities with typical xerophytic leaves, blackbrush leaves are more similar to typical semi-arid coastal chaparral plants in Mediterranean and southern California, or cool and high elevation inland desert perennial plants. Semi-deciduous, thick blades, well-cutinized epidermises, numerous small leaves, sclerophyllic leaves, hypostomatry, sunken stomata, thickened epidermal cell walls, and abundant abaxial and adaxial trichomes are characteristics of blackbrush plants, as well as typical woody xerophytic and sclerophyllous plants. Blackbrush also exhibit summer dormancy, with characteristics of revolute margins, uniseriate hypodermis, biseriate epidermis, bifacial palisade parenchyma, and intercellular air space in leaves; all of which are characteristics of leaves from sclerophyllous chaparral plants. Overall, xerophytic and sclerophyllous leaf designs are similar among blackbrush, warm desert plants, and semi-arid coastal chaparral plants, presumably due to many climatic and edaphic attributes shared by the inland Mojave Desert and coastal southern California. Because of a lack of consensus in current literature, morphological and anatomical characteristics of blackbrush leaves continue to be a curious dilemma to many botanists and plant ecologists.
