THE SEED. 



85 



a kind of involucre, as in tlie burr of the Chestnut, and 

 tlio cupule of the Oak, fig. 8. 



486. The Samara may he termed either a nut or 

 achenium, with a winged margin, as in the Birch. The 

 fruit of the Maple, fig. 14, is a twinned samara. 



487. The Pyxis is a capsule, opening transversely by 

 .. kind of lid, as in the Scarlet Pimpernel, fig. 7. 



MULTIPLE OR COLLECTIVE FRUITS. 



488. These are usually produced from a dense assem- 

 blage of flowers, united with their envelopes, and seated 

 on a more or less convex and elongated receptacle, the 

 whole mass of which, generally becoming more -or less 

 pulpy and edible, forms the fruit. They are either fleshy, 

 as in the Bread-fruit and Pine-apple ; pulpy and juicy, as 

 in the Mulberry ; or composed of dry and scaly bracts, 

 covering one or more naked seeds, as in the fruit of Pines. 



489. The Fio is a multiple fruit, composed of nume- 

 rous flowers inserted on a hollow receptacle, by which 

 they are completely inclosed. What are called the seeds 

 are, in fact, achenia, with their persistent style and stigma. 



490. The character of the Fig is completely re- 

 versed in the Mulberry, which has been compared to a 

 Fig turned inside out. 



491. The Cone (strohilum) is composed of dry or 

 horny scales, each of which forms an open carpel, bearing 

 one or more naked seeds, as in the Pines, fig. 4, Plate 

 XXVIII. The fruit of the Hop, fig. 2, is a cone, with 

 dry, membranaceous scales. 



492. The Pine-apple, fig. 1, is nearly related to the 

 cone in structure, the chief difference seeming to be that 

 the latter has neglected the development of pulp. The 

 bracts at the summit of the Pine-apple, not being ex- 

 hausted, like those below, by the production of pulp, be- 

 come expanded. 



493. The adhesion of two flowers sometimes forms a 

 double or twinned fruit, as in the beautiful little Par- 

 tridge-berry of our woods, and several species of Honey- 

 suckle. The principal difference between Multiple and 

 Aggregate fruits is, that the former are produced from 

 an assemblage of many flowers, the latter from a single 

 flower. At figs. 3 and 6 are fruits of a Moss and a 

 species of Fern. 



CHAPTER XXX. 



THE SEED. 



Difference between Multiple and A^j^egate fruits? Instances of each. How 

 are twinned fruits formed ? Instances. 



Ocueral subject Elementary Composition. Parts. Which sometimes 

 wanting? Name the Integuments. What is the outer commonly called— the 

 Inner? Describe thoEpisperm. How in the Milk-weed — the Cotton plant? 



494. Elementary Composition. — The seed consists 

 of cells, and the nutritive substances which are stored 

 up in them, for the nourishment of the young plant. 



495. Structure of the Seed. — The seed usually is 

 composed of three parts, the Integuments, the Albumen, 

 and the Embryo. The second of these is sometimes wanting. 



496. The Integuments. — The external or proper 

 seed-coat is called the Episperm, or more commonly the 

 Testa, and the inner is the Endosperm, or Tegmen. In a 

 section from the seed of the Pea, fig. 10, te is the episperm, 

 e the endosperm, c the fleshy cotyledon, andgr the embryo. 



497. The Episperm. — This membrane exhibits a 

 great variety of forms, colors, and degrees of smoothness. 

 It is winged in the seeds of the Trumpet-flower and the 

 Pine tribe, as in flg. 7, which represents a seed of the 

 Fir — ^bony in the Nutmeg ; and in many plants it is fur- 

 nished with a hairy .appendage, which by rendering the 

 seeds buoyant, or attaching them to other bodies, aids in 

 their dispersion. In the Silkweed it is covered with a 

 tuft of hairs called the coma ; and in the Cotton-plant 

 the whole seed is enveloped by a soft wool, which gives 

 its name and economical value to the plant. A single 

 fibre of cotton is seen at fig. 13, and one of wool at 14, 

 both greatly magnified, and showing the difierence of 

 structure. The pappus of the Compositse should not be 

 confounded with the hair that invests the seed, it being, 

 in fact, the calyx, and an appendage of the pericarp itself. 



498. The Endosperm is the inner integument, but 

 is often so strongly adherent to the episperm as to be in- 

 distinguishable from it ; and sometimes it is not present. 

 It is seen at e, fig. 10, while at te is the episperm. 



499. The Nucleus, or kernel, is the essential part of 

 the seed, and consists of the Albumen, when that sub- 

 stance is present, and the Embryo. About the time of 

 flowering the nucleus becomes hollow ; and after fertiliza- 

 tion the embryo is deposited in the cavity. The integu- 

 ments of the ovule are open at the summit of the nucleus ; 

 and through this opening, which is called the Foramen, 

 or Mycropyle, the fertilizing influence of the pollen is 

 admitted to the nucleus. This point, which is seen at m, 

 in fig. 10, always indicates the root end of the embryo. 

 The Chalaza, ch, is that point through which the fibrous 

 vessels, rap, communicate between the nucleus and the 

 integuments. 



Distinction between seed-down, and Pappus. Describe Endosperm— is it al- 

 ways present — apparent ? Essential part of the seed — of what consist — ^liow 

 about the time of flowering — what after fertilization ? Opening at the summit 

 of the Nucleus — its synonym — oflice— position ? Name the utalk of the seed. 



