This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
Variation is the rule with seeds as well as in all other natural productions. Those which belong to a particular family or genus may have sufficient general resemblance to enable us to determine the group to which they belong, still they will usually vary considerably in their general form. "As near alike as two peas," is a very common expression with people when comparing any two things which resemble each other very closely; still we may safely assert that no two peas are exactly alike.
In the great font of nature there is in-finite wisdom, and nowhere can we find it more wonderfully manifested than in the vegetable kingdom.
No two things are created just alike, and variation to a certain extent appears to be as much a fixed principle in nature as order and uniformity.
By examining the seeds of any of the great families of plants we will find a similarity between the different members, yet they are all distinct.
The oaks produce seed which vary greatly in size and form, still they are readily recognized as belonging to one family. No one would mistake an acorn for a hickory nut or beech nut. In structure, the acorn is not particularly different from some other seeds; it has the two fleshy cotyledons, resembling very much the chestnut, or even the common garden bean; and when placed under proper conditions for growth, the covering which incloses the seed proper, divides lengthwise, as shown in fig. 65, the root descending and the stem ascending, as shown. The bean grows in the same manner, but with this slight exception: the cotyledons are carried up and adhere to the stem, thus forming the lower or primary pair of leaves, fig 66, while in the acorn they are stationary, and usually remain within the half-opened shell until they decay.
In fig. 67 is shown an acorn, natural size, of the stalked fruited oak (Quercus pedun-culata). Fig. 68 is one of the upright oak (Quercus pedunculata fastigiata); and in fig. 69 is shown the form of the acorn of the Dyer's oak (Quercus tinctaria). These three illustrations will give a general idea of the variations to be met with in the seed of the oaks.
The horse-chestnut (AEsculus) produces seeds of a very similar structure to the oak, and yet they are different both in size, form, etc. The seed envelope, when germination takes place, does not burst open in a regular manner as in the acorn, but is torn asunder by the swelling of the cotyledons; and the stem and roots shoot forth, as shown in fig. 70. There are many other seeds of similar form and structure to those I have mentioned, but the number is far too great for me to attempt their enumeration here.
The hickories and similar nut-bearing trees produce seed inclosed within two very distinct coverings. The exterior one is of a husk-like material. The second, a hard, brittle, horn-like shell, and within this a fleshy substance, which is the seed proper. The black walnut, butternut, and English walnut are familiar examples of this kind of seed. Fig. 71 shows an English walnut (Juglans regia) entire, with the exterior coat removed, and fig. 72 the seed deprived of both coverings.
If we pass from the nut-bearing trees to other families, we observe a great change in form and structure of the seeds. The maples have what is called winged or key seed (Samara). They are usually produced in pairs, fig. 73, each pair being the product of one flower. The thin, membranous appendage is of no importance to the seed, except assisting in scattering them more widely when falling from the tree than they would be if they were formed without it.
The ash (Fraxinus) produces another form of winged seeds - fig. 74. The seeds of the ash are one or two celled, and the cotyledons are elliptical, and extend lengthways of the seed, not compressed into one end, as seen in the maple. A section of a seed cut across the center is shown in fig. 75. The elms have winged seeds of quite another form, the membrane in these passing entirely around. Fig 76, a seed of the cork bark elm (Ulmus campestris suberosa). Fig. 77, Ulmus campestris; and fig. 78, the Ulmus effusa. Other trees produce seeds covered with a thin pulp, like the common cherry or the nettle-tree. Fig. 79, Celtis occidentalis.
Most of our common evergreen trees, such as the pines, spruce, arborvitses, etc., have winged seeds. Some arc very small, while others are large; no true species producing seeds alike, although they are often very similar. Sometimes the chief difference will be in the covering, or in the manner in which they are produced. The least variation is important to the botanist in determining species and varieties, but of little consequence to the propagator so far as assisting him in' multiplying the plants, although he is expected to know wherein a variety or species differs from another of the same genus. If he does not know this, he will not be a very reliable propagator, because should his plants become intermingled by accident or otherwise, he would not be able to separate them.
In descending the scale from trees to shrubs, perennial, herbaceous, or annual plants, we will find the same variation in the form and structure of the seed. The treatment, however, to secure growth, is not so variable as the form, although it is sufficiently so as not to allow of any general rule that will be applicable to all kinds; therefore each great family or group requires a process particularly adapted to itself.
[to be continued.]