A Histogenetic Study of Foliar Determination in Carya buckleyi Var. Arkansana

Leaf Arrangements in Ailanthus Altissima

“…Schwendener (1878Schwendener ( , 1901) accepted Hofmeister's theory that each new primordium develops in the largest gap between the previously formed primordia. Snow and Snow (1931, 1933, 1935, from numerous experiments, obtained results in support of the Hofmeistervan Herson theory of phyllotaxis. Van Herson (1907) has offered the best explanation in support of Hofmeister's theory.…”

Evidence of microevolution in an escaped pear population

“…ters with normally distributed variation ranged from 7% to 40% ( elongation and therefore are more readily modified than characters determined within the primordia (Foster 1935(Foster , 1936Gregor 1938). Thus, while we might consider the skewed distribution in this case as evidence of marked selection for a resistant genotype, there is no evidence that most trees are not escaping infection by chance alone.…”

“…It has been noted that environmental modification working through the phenotypic plasticity may contribute as much to total variability in outbreeding populations as may recombination (Stebbins 1950). The latter two groups are determined within the primordia at an early developmental stage; easily modified characters on the other hand are determined du.ring cell elongation (Foster 1936). Clausen (1940) considered that the size of vegetative parts was most easily modified, the 'This investigation was part of a thesis submitted by the senior author in partial fulfilment of the requirements for a M.Sc.…”

The Initiation and Determination of Leaves.

“…Classic surgical experiments performed over 40 years ago established that the initiation of leaves by the shoot apical meristem does not depend on the presence of existing leaf primordia or other, more mature tissues, but that existing primordia can influence the positions of new primordia (Snow and Snow, 1931,1933,1935Ball, 1951). Because thesesurgical manipulations could have changed the space available for leaf formation on the apical meristem, these and other experiments have led some authors to adopt the view proposed as early as 1907 (Iterson, 1907) that a leaf primordium is centered on the first space within the organogenic region on the flanks of the apical meristem that becomes available as the shoot apex grows (Snow and Snow, 1962;Sachs, 1991).…”

“…Juvenile leaves are usually smaller and simpler than their adult counterparts and may differ in many other respects as well. For example, juvenile maize leaves are not only shorter and narrower than adult leaves, but they have epicuticular waxes not present on adult leaves, their epidermal cells are of different shapes than those of adult leaves, and they lack the hairs present on adult leaves (Poethig, Although juvenile leaves were initially thought to be developmentally arrested forms of adult leaves (Goebel, 1900), comparative developmental analyses of the two leaf types in severa1 species have demonstrated that juvenile leaf primordia are usually smaller and morphologically distinct from their adult counterparts at, or shortly after, inception (Foster, 1935;Kaplan, 1973Kaplan, , 1980Franck, 1976). The transition from the juvenile to the adult phase of shoot development is also marked by the transformation of the shoot apical meristem to a larger, morphologically distinct adult form (Abbe et al, 1941;Stein and Fosket, 1969;Kaplan, 1973;Franck, 1976;Greyson et al, 1982), and this correlation has led many authors to the view that juvenile versus adult leaf identity is determined at inception by the developmental state of the meristem itself.…”