INTERNAL STRUCTURE 



FIBROVASCULAR BUNDLES 



Cutting pomes to show the internal structure. 



When varieties cannot be distinguished from 

 external marks, there are several very reliable 

 characters that can be made use of in the in- 

 ternal anatomy of the pome. To study these 

 characters it is necessary to make a longi- 

 tudinal and a transverse section of the fruit. 

 To make an accurate examination of the in- 

 ternal structure of apple, pear or quince, the 

 sectioning must be done with a keen, thin 

 knife, with a steady hand and a good eye. 



In making the longitudinal section, the knife 

 should pass through the center of the calyx, 

 showing the remnants of styles and stamens; 

 through the middle of the core cell, showing 

 the outline of the core cavity; and through 

 the middle of the stem. A true record cannot 

 be obtained unless the organs named are di- 

 vided with fair accuracy into halves. In mak- 

 ing the transverse section, the knife should 

 pass through the widest diameter of the fruit, 

 cutting the core in half. If the core is not 

 in the center of the fruit, trial cuts to locate 

 it must be made that it may be halved exactly. 



2. Longitudinal section of an apple showing 

 core characters (X Vz). a, Cavity; b, core- 

 lines; c, abaxile open core with broadly ellip- 

 tical mucronate carpels; d, conical calyx- 

 tube; e, calyx-lobes; /, basin. 



The stamens. 



After halving the fruit longitudinally, the 

 first organs to be studied are the stamens, the 

 position of which furnishes reliable taxonomic 

 data. Hogg, an eminent British pomologist, 

 devised an analytical key to varieties of apples 

 based on the position of the stamens. Apples 

 may be divided into three groups in accordance 

 with the position of stamens. In one group 

 the stamens are on the outer margin of the 

 calyx-tube and are said to be marginal; in 

 the second, they are located about the middle 

 of the tube and are said to be median; in the 

 third, they are inserted at the base of the 

 tube and are said to be basal. 



The calyx-tube and styles. 



Passing from the stamens to the calyx-tube, 

 it will be found that the shape of this structure 

 is of some use in separating varieties, although 

 it is exceedingly variable in accordance with 

 the size of the fruit, and is materially altered 



by abnormalities in the fruit. The base of the 

 styles, in some varieties, develops into fleshy 

 tissue which alters the shape of the calyx-tube. 

 The calyx-tube may be cone-shaped, funnel- 

 shaped, or urn-shaped. When funnel-shaped, 

 the broad upper part is called the limb; the 

 narrow lower part, the cylinder. In some 

 varieties the remnants of the styles, often more 

 or less fleshy, form a point, called the pistil- 

 point, which projects into the calyx-tube. 

 Gano has a well-developed pistil point. 



The core. 



The position of the core in the fruit is 

 often a valuable means of distinguishing varie- 

 ties. If close to the stem, the core is said to 

 be sessile; if at the center of the pome, it is 

 median; when distant from the stem, distant. 

 The cell containing seed, called a carpel, is 

 morphologically a modified leaf, which by 

 folding together and by union of its edges 

 forms a closed receptacle. In some varieties 

 the carpels are open; in others, closed. If the 

 tip of the carpel is indented, it is said to be 

 emarginate; if long and pointed, mucronate. 

 In shape, carpels may be round, cordate, ob- 

 cordate, elliptical, oblong, elongated, ovate, or 

 obovate. In the cores of most pomes there 

 is a central cavity called the core-cavity, some- 

 times spoken of as the axial-sac, which may 

 be either narrow or wide ; in some it is lacking. 

 This is a character of much importance and 

 reliability in pears. When the carpels extend 

 quite to the axis of the fruit, they are said 

 to be axile, and there is no core cavity; when 

 distant from the axis, they are abaxile, and a 

 core cavity is formed. Sometimes the carpel 

 is lined on the inner surface with a white sub- 

 stance, as in Tompkins King, when it is said 

 to be tufted. In some pears there are many 

 fine hairs in the core-cavity, in which case the 

 cavity is said to be tufted. The characters of 

 the core are shown in Fig. 2. The limits of 

 the core are marked by a line usually very 

 distinct in apples and quinces, which is called 

 the core-line. The area enclosed by this line 

 may be large or small and may be variously 

 shaped. In some species of apples, as in 

 P. coronaria and P. ioensis, rue core separates 

 from the flesh along the core-line so that it 

 may be taken out, leaving a well-defined cavity 

 in the apple. The direction which the core- 

 line takes from the intruded woody stem fibres 

 is often a clear mark of distinction. Thus, the 

 line may proceed at right angles from the 

 stem, may incline upward, or incline down- 

 ward. When the core-line joins the calyx-tube 

 along the sides it is said to be clasping; when 

 the two ends of the line meet at the base of 

 the calyx-tube, the expression "core-lines 

 meeting" is used. 



Fibrovascular bundles. 



Ten primary fibrovascular bundles enter the 

 flesh of pomes from the pedicel and closely 

 follow the core-line which marks the limits of 

 the core. These are plainly seen in transverse 

 sections of apples and quinces as well-marked 

 dots. They are arranged in two cycles. In 



