Chapter 2

The Plant Varieties and Seeds Act (1964)

This Act protects the rights of producers of new cultivars. The registration of a new cultivar is acceptable only when its characteristics are shown to be significantly different from any existing type. Successful registration enables the plant breeder to control the licence for the cultivar’s propagation, whether by seed or vegetative methods. Separate schemes operate for the individual genera of horticultural and agricultural crops, but all breeding activities may benefit from the 1964 Act. Producers of licensed plants pay a royalty fee to the breeder.

The meanings of plant names

Plant names, both generic and specific epithets, are derived from Latin or Greek. They can give useful information about a plant. By far the largest group of names are descriptive ones. Some types of names are listed here.

Commemoration

These are given to commemorate the person who first found or bred the plant or as a reward for patrons of plant collectors and breeders. Sir Joseph Banks, for example, was a wealthy British naturalist from Lincolnshire, who, as a result of his membership of Captain Cook’s first voyage which included Australasia in the 1760s, brought to the West eucalyptus, mimosa and the genus Banksii. He had a large botanical collection and some eighty plant species bear his name as a result of many journeys, including North America and the British Isles. Banks was responsible for organising the first Kew collections whilst supervising the development of Kew Gardens. Some of the species named after Banks include Grevillea banksii, Cordyline banksii, Astelia, banksii, Columnea x banksii, Banksii integrifolia, Banksii serrata.

Other examples include:

• Saintpaulia, named after Baron Walter von St. Paul, who discovered it.
• Abelia, named after Dr Clarke Abel who discovered Abelia chinensis in China.
• Berberis darwinii after Darwin.

Season or life cycle (specific epithets)

Helianthus annuus – annual

Bellis perennis – perennial

Crocus vernus – of spring

Rhododendron praecox – early

Buxus sempervirens – evergreen

Uses or properties (specific epithets)

Rosmarinus officinalis – of the (apothecary’s) shop

Passiflora edulis – edible

Betula utilis – useful

Papaver somnifera – sleep inducing

Cytisus scoparius – of brooms or brushes

Daphne odora – very fragrant

Habitat or origin (specific epithets)

Ranunculus alpestris – of the lower Alps

Erinus alpinus – of the high Alps

Cymbalaria muralis – of the walls

Acer campestris – of the plains

Griselina littoralis – of the seashore

Caltha palustris – of the marshes

Pinus sylvestris – of the woods

Poa pratensis – of the meadows

Galanthus nivalis – of the snows

Erysimum muralis – growing on walls

Habit, size or shape (specific epithets)

Betula pendula – weeping

Betula nana – dwarf

Vinca minor – small

Vinca major – large

Philodendron scandens – climbing

Juniperus procumbens – trailing

Rubus fruticosus – shrubby

Hedera helix – twining

Ajuga reptans – creeping

Betula pendula – drooping

Echinops humulis – low growing

Flower colour (specific epithets)

Cornus alba – white

Helleborus niger – black

Digitalis purpurea – purple

Passiflora caerulea – blue

Centranthus ruber – red

Gentiana lutea – yellow

Leaves (specific epithets)

Arum maculatum – spotted

Lavandula angustifolia – narrow

Alchemilla mollis – soft

Hebe salicifolia – like a willow

Acanthus spinosus – spiny

Viburnum plicatus – folded

Solanum crispum – wavy edged

Hydrangea macrophylla – large leaved

Bergenia cordata – heart shaped

Lonicera nitida – shiny

Hibbertia dentata – toothed

Helleborus argutifolius – sharply toothed

Galium longifolium – long-leaved

Galanthus latifolius – broad-leaved

Clematis integrifolia – entire leaves

Reproduction in conifers e.g. Pinus sylvestris

Conifers such as Pinus sylvestris belong to the gymnosperm (‘naked seed’) group of the Plant Kingdom because their ovules which later become seeds are borne exposed on the scales of cones. They do not produce flowers or fruits. Conifers are important both for amenity use and also as a source of timber. Their wood is mostly softer and more easily worked than that of broadleaved ‘hardwood’ trees hence the name ‘softwoods’. Many grow fast on poor soils and in harsh climates and show adaptations for drought resistance (xerophytic adaptations) such as reduced leaves or needles. Conifers originate in the temperate zones of the world and on mountain ranges in the tropics.

Britain has only three native conifers: Pinus sylvestris (Scots Pine), Taxus baccata (yew) and Juniperus communis (juniper). Apart from yew, which belongs to the family Taxaceae, the majority of native and introduced species belong to the large family Pineaceae.

The life cycle of Pinus sylvestris

Pinus sylvestris is a monoecious tree bearing male and female cones on the same plant. Pollen is produced in small, short-lived male cones (strobili) which are borne in clusters, a short way down the branches (Figure 1.) Each male cone contains microsporophylls which bear microsporangia (pollen sacs) in which pollen grains develop. The nucleus of each pollen grain divides to produce three haploid nuclei (a sperm nucleus and two male gametes). Pollen grains are released in May over a few days when all the cones on a tree shed their pollen together. The male cones soon disintegrate after pollen release and are not retained on the tree.

The pollen is carried by the wind to the larger, female cones (Figure 2a and b) which are borne on the shoot tips. Female cones are made up of cone scales (ovuliferous scales or megasporophylls) which, in Pinus sylvestris, bear two ovules on their lower surface each containing a female gamete. A whorl of cones is produced in each season so a season’s growth is found between cones along a branch. In their first year, the scales on female cones open to receive pollen and are receptive for around 2–3 days at the same time as pollen dispersal. Once pollination has taken place the female cone closes tightly, to protect the developing seed within. Initially the purple tinted female cones are only about 0.6–0.7 cm in length and for 12 months the germinated pollen grain remains dormant. The following year, the pollen tube resumes growth and fertilization takes place. In this second year, during which the female cones remain closed, the cones ripen and the seed matures with the female cone growing in size and turning from green to brown following fertilization. Unlike the double fertilization which takes place in flowering plants, a single fertilization occurs to form the zygote which gives rise to the embryo in the seed with the second male gamete disintegrating. Seed is shed in the spring of the third year following alternating periods of dry and wet weather. The scales open again to release the ripe seed which is dispersed by the wind aided by papery wings made up of part of the cone scale. The female cone may subsequently fall or be retained on the tree.

The immature male and female cones are sometimes referred to as ‘flowers’ but these are not equivalent to the flowers and fruit produced by broadleaved trees which belong to the Angiosperm group of the Plant Kingdom.

Figure 1 A cluster of male cones of Pinus sylvestris

Figure 2a Female cone of Pinus sylvestris after pollination in its second year

Figure 2b Mature cones of Pinus sylvestris showing cone scales after seed is shed in the third year. The position of the two seeds can be seen as shallow, darker coloured depressions in the surface of each cone scale

Distinctive characteristics of conifers

Conifers may be distinguished from broadleaved trees by the following features:

• Narrow, needle-like or scale like leaves.
• Foliage usually evergreen exceptions being the genera Larix (the larches)and Taxodium (the swamp cypresses).
• Scaly buds which are often resinous.
• A regular almost geometrical branching habit.
• Resinous fragrance of foliage, buds, bark and timber and resin produced in specialized cells or ducts in the timber.
• Xylem tissue containing tracheids rather than xylem vessels. Phloem tissue with albuminous cells replacing companion cells.
• Male and female cones produced separately, though usually on the same tree, wind pollinated, no flowers produced.
• Seeds borne on woody cone (or rarely a fleshy structure called an aril as in Taxus baccata (yew) or Juniperus communis (juniper)).
• Seeds usually winged and dispersed by wind.
• Seedlings have two or three or numerous seed leaves or cotyledons depending on the species.