This section is from the book "The Fruit Manual: Containing The Descriptions And Synonyms Of The Fruits And Fruit Trees Of Great Britain", by Robert Hogg. Also available from Amazon: The Fruit Manual.
Many attempts have been made to devise a classification for the Apple. Diel, Bidder, Dochnahl, Lucas, and others have each produced one, but they are all modifications or altered forms the one of the other, and the characters upon which they are constructed are too inconstant and indefinite to render their work of much practical utility. As the ultimate design of classification is mainly to facilitate the identification of the numerous objects that are the subject of inquiry, if it fails in this, much of its usefulness is impaired. The systems to which I have alluded have all proved failures, and, with the exception of Diel's and Dochnahl's, I am not aware that under either of them the numerous varieties of Apples have ever been classified.
In British Pomology, which was published many years ago, I suggested a classification for the Apple that was intended to lead to the discovery of the names of the different varieties described in that work, but its scope was too limited, and it consequently failed in its purpose. Previous to this I had attempted to make use of Diel's arrangement, but without success, and then I resolved to search out for myself characters upon which to base a system that would accomplish what I had in view.
In 1876 my earliest views of a new system were published in The Journal of Horticulture. It appeared while I was absent from home, and was set up in so confused a manner that it called forth some well-merited criticism. I reconstructed it in what I conceived to be a better shape, and it was printed in a distinct form as A New Classification of Apples. This is the basis upon which my new and amended system is founded. I find, however, that in this as in every other classification of natural objects there are the usual difficulties to contend with. Nature refuses to be bound, and will not submit to be confined, within the narrow limits that man would assign to her. There is still the debatable ground to deal with, where there are no definite boundaries and we are met on every hand by the difficulties experienced by M. Milne-Edwards, who says, "We sometimes see the transition of one plan of structure to an entirely different scheme of organisation take place by degrees so completely shaded one into the other that it becomes very difficult to trace the line of demarcation between the groups thus connected;" and it must always be so. No classification of natural objects has yet been constructed on perfectly fixed principles, and if we were to wait, expecting to arrive at that state of scientific accuracy, we should continue waiting. Every system now in use has been crude in its beginning. The natural system of botany, for instance, which is now almost universally in use, was evolved, and is still being evolved, out of one which "abounded in errors and imperfections." I am not discouraged, therefore, when I meet with difficulties in applying my system. I feel assured that after it has been put into operation, and some of its imperfections have been discovered and have disappeared, it will eventually be found to answer the purpose for which it is intended; for I am convinced that the principles upon which it is founded are sound.
The structural characters on which this classification is based are - 1. The Stamens; 2. The Tube; 3. The Carpels; and 4. The Sepals.
When we make a longitudinal section of an Apple through the centre of the eye to the stalk we see these various organs. At the top of the section are the calycine segments, or what is technically called the eye, and immediately below them there is a cavity called by botanists the flower-tube. Inserted in this tube is a ring of small bristle-like organs, which are the remains of the stamens, and these occupy three different positions. In some fruits they are very near the top of the tube; in others they are lower down, and occupy a position about the middle; whilst in others they are very near the base. The tube itself is of two forms - the conical and the funnel-shaped. Just below the tube is the core, composed generally of five cells or carpels, and these assume four different forms - round, ovate, obovate, and elliptical; and each of these varies in its relation to the axis of the fruit, some extending close to it and forming symmetrical cells, while others are distant from it and are unsymmetrical.
These being the principal characters with which we have to deal, I shall now proceed to treat of them individually.
1. The Stamens. - I have already stated that these occupy three different positions in the tube, and I have adopted them as the primary divisions of this system, having found by experience that they are on the whole the most reliable characters where all are more or less changeable. The marginal position is shown in Figs. 1, 2 a, 3, and 4 a ; the median in Figs. 5 a, 6 a, and 7 ; and the basal in Figs. 8 a and 9 a.
2. The Tube. - The tube is of two distinct forms - the conical and the funnel-shaped - and these are more or less modified in shape, as will be seen on reference to the various diagrams. The outlines of the conical tube, as shown in Figs. 1, 2, 6, and 9, proceed from the base of the sepals in a curved line downwards towards the core, forming an inverted cone. These curves are generally inwards, but occasionally they are outwards, as in Fig. 1, which has suggested to me the formation of another division under the name of urn-shaped; but it occurs so seldom that no importance need be attached to it. The lines of the funnel-shaped tube proceed, like those of the conical, from the base of the sepals, curving outwards in the same downward direction, and then, curving inwards, form a hump or shoulder which is higher or lower than the middle of the tube; and this has the appearance of a funnel shape, as is shown in Figs. 3, 4, 5, 7, and 8.
3. The Carpels. - These constitute what is popularly called the core of the apple. They are generally five, occasionally they are four, and I have seen only three, but this is very rarely met with. These carpels or seed-cells vary in shape. If one is split down the middle its walls or membranous lining will be either round, as represented in Fig. 2 b; ovate, as in Fig. 6 b; obovate, as in Fig. 9b; or elliptical, as in Fig. 4 b. Then in relation to the axis of the fruit, they are either axile or abaxile. When the walls extend to the axis, and these characters will be best seen by making a transverse section of the fruit, the cells are symmetrical, as shown in Figs. 10 and 11, and then they are said to be axile, whether they are open, as in Fig. 11, or closed, as in Fig. 10. When they are distant from the axis, and the cells are unsymmetrical, as shown in Fig. 12, they are called abaxile.
4. The Sepals or Eye. - These are a portion of the remains of the flower, which in their original form, when accompanied by the corolla, were uniformly expanded and spreading. After the petals drop, and as the fruit develops, they gradually assume various directions, and when it is perfectly matured we find them in four distinct forms. The first of these is shown in Fig. 13, where the segments are quite reflexed, frequently so much as to fall back flat on the fruit in the form of a star; they are then said to be divergent. In Fig. 14 we have another form, in which the segments are never reflexed, but are erect with their margins merely touching and their points divergent; and these are erect convergent. Then there is the flat convergent position (Figs. 15 and 16), in which the segments are flat, closing the eye, but with their margins merely touching and not overlapping each other. And lastly we have the connivent form (Figs. 17 and 18), in which the segments are all close together, overlapping each other and forming a compact cone.
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The minor divisions require no great explanation. They classify the fruit according to form as they are round or oblate, conical or ovate, and these again are further divided according to their surface colouring. This latter character requires a little explanation. When fruit is said to be pale it signifies that it is of an uniform colour of yellow or green, notwithstanding that it may be faintly tinged on the Bun side with orange or pale red. It is said to be striped when the only additional colour to that of the ground colour consists of distinct red stripes without any ground colour of red. It is said to be coloured when the skin is wholly or partially a decided red, and this may be accompanied with stripes or with some russet. The russet skin is that in which a russet coat prevails. When a russet coat has a brown or red cheek the fruit is not on that account to be classed in the coloured section. In every case I have indicated the time of year during which the fruit is in use as a further help to the identification of it.