Some Technical Terminology

Lois E. James

Professor Emeritus Biology, Whittier College, Whittier, CA

Reprinted from the CMS Yearbook 1971

It has been suggested that certain terms used in the yearbook be explained. A request from members for this year included the following.

BIPINNATE.  See Pinnate.

CAMBIUM.  A single layer of cells between the xylem (water conducting tissue) and phloem (food conducting tissue). The cells of the cambium divide to produce more xylem and more phloem cells When the bark (cork plus phloem) is peeled off as in girdling, the place of rupture is the cambium. A girdled area exposes the xylem or wood.

CLONE.  Descendents of an individual plant produced asexually. For example, Elimbah trees constitute one clone and they may be obtained from grafting, budding, or from cuttings.

CRACK-OUT.  A term used to describe the comparative weight of shell and kernel. Crack-out is expressed as percentage of kernel. Therefore a crack-out of 30 means 30% of the weight of the nut is kernel and 70% is shell.

DEHISCENT.  Refers to dry fruits, which split open at maturity. The husk, which is the fruit in macadamias, is dehiscent.

DENTATE. Sharp coarse teeth perpendicular to the margin. Some Macadamia trees have leaves with dentate margins.

GIRDLING.  Removal of a ring of bark from around the stem. This removes the phloem but the xylem is not disturbed, and water readily passes up the stem. Removal of the phloem prevents the sugar manufactured in the leaves from moving down the stem past the girdled area.

INDEHISCENT.  Commonly refers to dry fruits, which do not split open at maturity. A true nut like a hazelnut is INDEHISCENT.

INFLORESCENCE.  Flower cluster.

LEAF WHORL.  Refers to the group of leaves at any one "joint" on the stem. Commonly M.integrifolia has 3 leaves at each "joint" and M. tetraphylla has 4.

MEIOTIC METAPHASE.  A stage of division of cells producing pollen and cells producing eggs In this stage the chromosomes are most easily counted.

MEIOTIC NUMBER. The number of chromosomes characteristic of the egg or of the sperm in the pollen grains. The meiotic number of macadamias is 14.

MITOTIC NUMBER.  The number of chromosomes found in the cells of the plant, other than in pollen grains and embryo sac. The mitotic number for macadamias is 28.

OIL CONTENT.  The amount of oil expressed as percentage of dry weight.

PEDICEL.  The stalk of an individual flower of a cluster.

PERIANTH.  A collective term for petals and sepals. In macadamia flowers the floral tube is made up of 4 coalesced sepals. There are no true petals although the sepals look like petals.

PETIOLE.  The stalk of a leaf. The leaves of M. integrifolia are petiolate but the leaves of M. tetraphylla do not have petioles and are called sessile.

PETIOLULE.  Stalk of a leaflet.

PERICARP.  The wall Of the fruit. In macadamias the pericarp is the husk.

PINNATE. Parts arranged on opposite sides of a common axis. Macadamia leaves are pinnately veined since secondary veins branch out in parallel fashion from a single main vein. The term is used also to describe compound leaves. In a pinnate leaf as in Carob, the leaflets are in opposite pairs along the axis.

PHYLLOTAXY.  The arrangement of leaves along the stem. In macadamias commonly there are 3 or 4 leaves at a node or "joint." A node is the area along the stem, which bears the leaves. In the axils of the leaves are the branches or buds.

RACEME.  A flower cluster in which flowers, each with its own pedicel are spaced along an axis. The lower flowers bloom first.  

RACHIS.  The axis of a flower cluster or axis of a pinnate leaf.

ROOT STOCK.  The tree onto which a graft is made.

SCION.  A detached portion of shoot used in grafting.

SEEDLING.  A plant or tree grown from a seed as opposed to a budded or grafted tree or tree grown from a cutting.

STOMA (PL. STOMATA).  A pore or opening between 2 specialized cells called guard cells. The guard cells can swell and close the pore. Stomata are the openings through which carbon dioxide enters the leaf for photosynthesis and water leaves the plant in the form of vapor. The evaporation of water through the stomata is a major factor in pulling water and dissolve minerals up the tree.

TOPWORK.  Cut off the branches of a tree and graft onto the stumps.

TRANSPIRATION.  The giving off of water vapor from the plant.

TURGID.  Full, but not swollen.

VARIETY.  The botanical variety is a category of classification below species. A horticultural variety is a selection, which may be a minor variant, major variant, or hybrid. It is belie to be superior in some way and is established as a clone.