Seeds of Puerto Rican cycad, Zamia portoricensis. Susua State Forest, south-western Puerto Rico.

Ancient Seeds

SUPERDIVISION SPERMATOPHYTA: THE SEEDING PLANTS

    The other plants on planet Earth are the spermatophytes, which do not reproduce by spores, but by seeds.

    A seed is really a collective and quite complex entity: a store of varied amounts and combinations of fats, proteins, and carbohydrates, accumulated with the purpose of sustaining an embryo until it germinates as a seedling, and for a little time after. Once the resources of the seed are exhausted, the plantlet begins in earnest the process of photosynthesis that will sustain it for the rest of its life. The seed is protected by a covering, usually a flexible membrane, sometimes a woody encasement, that protects all that is inside. The nutrient store of the seed is to a plant embryo what the yolk of an egg is to an animal embryo.

    Because higher plants have lower metabolisms than most animals, many take years, even decades, to reach maturity. Some chlorobionts may live for centuries. The oldest living organism is believed to be a Great Basin bristlecone pine (Pinus longaeva), in North america. Its age was possibly 4862 years at the time of its destruction. A clonal colony of quaking aspen, Populus tremuloides, located in the United States might be one million years old.

    Since most plants keep growing throughout their entire lives, some can grow to gigantic sizes, rivaled by those of no known animals, alive or extinct. The largest living organisms are conifers: the coastal redwoods (Sequoia sempervirens) and the giant sequoias (Sequoiadendron giganteum) of western North America. Both can grow to be more than 100 meters tall, and weigh hundreds of thousands of kilograms. The biggest single (non-clonal) organism known is "General Sherman", a giant sequoia.

    The living representatives of this enormous group are separated into three divisions: Divisio Cycadophyta (cycads and their relatives), Divisio Pinophyta (= Coniferophyta: pines, spruces and other cone bearers) and Divisio Magnoliophyta (= Angiospermae = Acanthophyta: the flowering plants).

THE NON-FLOWERING SEED PLANTS

    The more primitive of seed-bearing plants are the conifers and their kin, non-flowering plants that saw their heyday during the Mesozoic era. Also called "gymnosperms", the term means "naked seed", in reference to the fact that the egg of the plant is not enclosed at the moment of pollination, so the pollen enters into direct contact with it in order for fertilization to occur. Another trait of this group is that the seeds are never enclosed in a true fruit, as they develop. However, the seeds of some species may be covered in some king of fleshy structure.

    The eggs and developing seeds of many (not all) members of this division are often grouped into bulky, woody structures, the "cones" that so many people relate to these plants.

     Modernly, these organisms are not as abundant and varied as in eons past, and many are most common in temperate and sub-arctic forests, as well as in alpine ecosystems. In such environments they may be the dominant chlorobiontic life-forms, at least in terms of biomass.

    There are several divisions within this group, but relatively few species are found in tropical regions, where they have to compete for resources with the - presently far more successful - flowering plants.

DIVISION CYCADOPHYTA: CYCADS AND THEIR KIN

    There are few cycads in the West Indian region. These are primitive cone-bearing plants, with stout (if sometimes very short) trunks, and crowns of composite leaves. They are of wide distribution in the Old and New worlds. Those of the genus Zamia, (family Zamiaceae), resemble ferns in general appearance. They are small to medium-sized and are found in forests' understories.

Zamia ambliphyllidia.

First photograph: Cerro Las Cuevas, southern Puerto Rico.
Last two photographs: Cambalache State Forest, northern Puerto Rico.

The members of this family are rather primitive plants which are distantly related to pines.

Zamia portoricensis. Susua State Forest, south-western Puerto Rico.

Zamia debilis. Parque Nacional del Este, eastern Dominican Republic, Hispaniola.

Zamia sp. National Botanical Garden, Santo Domingo, south-western Dominican Republic, Hispaniola.

Zamia erosa. Los Haitises National Park, northern Dominican Republic, Hispaniola.

DIVISION PINOPHYTA: PINES, SPRUCES, AND THEIR KIN

Order Pinales: Pines and their Kin

    Many of the extant species of this group - like the families Pinaceae (pines) - are nowadays more common in the temperate zones of Earth and in tropical montane regions, like the Himalayas and the Andes. A few live in the West Indies, particularly the several species of Pinus of the Bahamas, Cuba, and Hispaniola. Pines form almost pure stands in some valleys of Hispaniola's highlands, reaching the summits of the tallest mountains.

    Due to substances in their resinous sap, pines can tolerate deep cold without loosing their leaves in winter (hence the term "evergreen"). That is one reason why the highest mountains in Cuba and Hispaniola, some of which commonly experience freezing temperatures in winter nights, have pines in abundance.

Order Podocarpales: Podocarps and Their Kin

    The seeds of these shrubs and trees are atypical among those of the division in being covered in a fleshy "pseudo-fruit". Their leaves are flattened, unlike the "needles" of most pines.

    Podocarps are rather picturesque trees found in the montane forests of the Antilles, as well as on the American continents. However there, and unlike West Indian pines, they are never the dominant species but are simply elements of the much more complex communities of montane rain forests and cloud forests.