Fern

"Ferns, encompassing approximately 12,000 species (PPG 1, 2016), represent only about 4% of diversity (Mehltreter, 2010); nonetheless, they provide important (Sharpe et al., 2010), and comprise a substantial portion of commercial ornamental plant production as well as horticultural economic development (Hoshizaki and Moran, 2001; Singh and Johari, 2018). Their evolutionary and paleobiological history is extensive beginning in the , approximately 390 million years ago (mya) with expanded diversity during the (65 mya), when s were becoming more dominant (Schneider et al., 2004; Schuettpelz and Pryer, 2009). Ferns were dominant flora in the , later losing space to s and angiosperms. Increasing forests provided suitable protective, shady environments where ferns flourished on the forest floor or as epiphytes on tree trunks and limbs (Watkins and Cardelús, 2012). Subsequently, over geological time spans, through adaptation and evolutionary radiation (Sessa, 2018), ferns proliferated to occupy a wide diversity of terrestrial environments; ranging from s and coastal locations to more open s, mountain terrains, and s. Consequently, their and life histories ... have commensurately expanded to include a rich panoply of different life forms, physiological adaptive strategies, and wide global habitats."

"' is not so happy-looking in cultivation as ', and it is even more troublesome to pack. I took up a large number of roots, sewed them in a flat package, and put them at the bottom of the box with the other Ferns upon them. In this way the fronds were injured, but the roots themselves were unharmed. About I found my first '—that loveliest of all our English Ferns—so easy of cultivation, so delicately varied in form, and yet so tenacious of life that the smallest division of the bulbous-looking roots will grow."

"s differ from s in the principles of their construction and growth. If we examine the base of a leaf-stalk of a tree we shall find a bud there, which, if left alone, will produce a branch or a cluster of fruit the next season. There are no such buds in the axils of fern leaves, not even in those of the , which is peculiarly tree-like in its growth. The growth of a fern is a sort of perpetual lengthening out at both ends. The upward growth, which is more frequently the subject of observation than the growth of the roots, consists first in a process of unrolling, and then of expansion and maturation of the leaves and stems. Because of these and other characters which obviously and without reference to the peculiar nature of their fruit distinguish them from flowering plants, the several parts of a fern are named differently to the corresponding parts in flowering plants. Thus, the true stem or root-stock of a fern is called a ', the true leaf is called a ', the stem which bears the leaf is called the ', and the ramifications of the stipes through the leafy portion corresponding to the leaf-stalks of other plants bears the name of '."

"1. s are most prominent in shady and humid environments, but many species are also found in drought-prone habitats, either (semi) arid ecosystems or locations with discontinuous water supply within otherwise humid ecosystems. These locations include tree branches and rocks, both substrates with little water storage capacity. 2. is gained through adaptations in water uptake, water loss, water storage and, in many ferns, , a feature that ferns share with other s. The little information available on the 's efficiency to limit water loss suggests that it may be similar to other s. Thus many ferns, while tolerating desiccation, normally avoid it through low cuticular and tal water loss and may not be considered truly . Exceptions are filmy ferns with very little control of water loss and whose water relations are akin to mosses rather than vascular plants. 3. Other adaptations found in xerophytic ferns include photoprotection with pigments, antioxidants, dense , leaf curling and drought avoidance by shedding leaves in the dry season. (CAM) is a common adaptation of xerophytic angiosperms, but is very rare in ferns. is not strongly developed in xerophytic ferns."

"The focus of shifted from simple descriptions to more detailed observations of and when Watt (1940) published the first of his many ecological studies of ' (bracken) in Britain (see Watt, 1976 for a review). Pteridium is an extremely successful colonizer worldwide and can form dense, nearly impenetrable stands. Pteridium generally contains several biochemical compounds such as high levels of s that make it health hazard when eaten by livestock or humans, although the early of New Zealand used ' s as a crop. Where it is unwanted (i.e., considered an invasive weed), Pteridium is difficult to eradicate. Pteridium therefore continues to be an important subject for ecological research (Robinson, 2007). Studies of Pteridium and other abundant ferns have helped to develop an understanding of the complex relationships between ferns and other environments."