Unit 14

GRAMMAR: INFINITIVE.

Texts: coniferophyta: conifers. Anthophyta / angiosperms: flowering plants. Pre-reading and reading tasks

1. Make sure you know the following words:

pine	[paIn]	сосна
spruce	[spru:s]	ель
fir	[fE:]	пихта, ель
hemlock	['hemlPk]	болиголов крапчатый
cypress	['saIprIs]	кипарис
redwood	['redwVd]	калифорнийское мамонтово дерево, секвойя вечнозеленая
larch	[lQ:tS]	лиственница
juniper	['dZu:nIpq]	можжевельник
yew	[ju:]	тис
ocher	['qVkq]	раструб
cone	[kqVn]	шишка
lure	[l(j)Vq]	приманка
seed	[si:d]	семя
pulp	[pAlp]	пулька, мякоть
dispersal	[dIs'pE:s(q)l]	рассеивание
sporangium (pl. –ia)	[spq'rxndZIqm]	спорангий, споровый мешочек
mitotic	[maI'tqVtIk]	митотический
ovule	['Pvju:l]	семяпочка
аrchegonium (pl. –ia)	["Q:kI'gqVnIqm]	архегоний
pine scale	[paIn] [skeIl]	щитовка сосновой хвои

2. Read and translate the text. Coniferophyta: conifers

Usually referred to as the conifers, this group includes pine, spruce, fir, hemlock, cypress, redwood, larch, juniper, and yew, as well as others that aren’t as well-known. The conifers include about 50 genera, comprising over 600 species. Their fossil history dates back to the late Carboniferous, some 300 million years ago. Although the cone is a conspicuous feature distinguishing many members of this group, it does not appear on all conifers. For example, juniper berries are actually small cones with fleshy scales. And yews have seeds surrounded at the base by a fleshy, berry-like pulp. In biological terms, the distinction between cones and more berry-like forms of reproduction is significant in terms of the mode of dispersal used by the conifers involved. The pinoids are adapted for wind dispersal of their seeds. The others are adapted to animal dispersal.

Trees are the diploid sporophyte stage of the life cycle. The cones are actually tight clusters of modified leaves known as the sporophylls, which, in the case of the pines, are also known as cone scales. Each sporophyll contains two sporangia in which haploid spores are produced through meiosis. These trees are heterosporous. The large female cones contain the sporangia that produce megaspores; the small male cones contain sporangia that produce microspores. All seed plants, both the gymnosperms and angiosperms, are heterosporous.

Each pine scale contains two sporangia; each sporangium has a small opening, the micropyle. Meiosis occurs inside the sporangium, producing four haploid megaspores, three of which disintegrate. The remaining megaspore, through repeated mitotic divisions, becomes the female gametophyte, which, unlike that in the ferns, is considerably reduced in size. It is located within the cone. The gametophyte is not free-living, nor does it contain chlorophyll. Each female gametophyte produces several archegonia in which egg cells develop. Together the entire structure consisting of the integument, the sporangium, and the female gametophyte is called an ovule.

Within the male cones are sporangia that produce microspores. These become pollen grains, which develop a thick coating, resistant to desiccation. They have small wing-like structures that help them along when carried aloft by the wind. Inside the pollen grains, the haploid nucleus divides mitotically and the pollen grains become four-celled. Two of these cells degenerate. When the sporangia burst, millions of mature pollen grains are released. This is the male gametophyte stage cycle.

Most of the pollen grains that land on the female cones fall between the scales. Some of these land near the opening of the micropyle. When a pollen grain lands touching the end of the sporangium inside the micropyle, it grows a pollen tube. The germinated pollen grain, which is now the pollen tube, grows down through the sporangium and penetrates one of the archegonia of the female gametophyte. There the tube releases its nuclei, which, in this case, are sperm that developed when the cells in the pollen tube were dividing. The sperm fertilize the egg and the resulting zygote produces an embryo sporophyte. This is still contained within the female gametophyte inside the pine cone. Finally, the cone sheds its ovules, more commonly known as seeds, which grow into adult sporophyte trees.