PYROLA 



PYRUS 



1469 



ginosa, Gray, with pink or rose-colored fls. and subcor- 

 date to obovate, dull Ivs., occurs in swamps, Arctic 

 regions, and as far south as Ga., New Mrx. and Calif. 

 Var. asarifolia, Hook., with purple fls. and round kid- 

 ney-shaped to ovate-orbicular Ivs., occurs northward. 



C. F. WHEELER. 

 PYEOLA, One-flowered. Moneses grandiflora. 



PYKU8 (Latin name of pear tree). Sometimes spelled 

 Pirns. Kosacece. POME FRUITS. Flowers normally 

 perfect, regular, in spring; torus urn-shaped and at- 

 tached to the carpels and finally closing over them, and 

 with them becoming fleshy in fruit; calyx-lobes 5 and 

 persistent upon the top of the young fruit, or in some 

 cases falling away at partial maturity; petals 5, white or 

 red; stamens 20 or more; pistils 2 to 5, crowning a 

 2- to 5-loculed ovary in which the locules are usually 

 2-seeded. Fig. 2018. Pyrus is a polymorphous genus, 

 comprising some 30 to 50 species in the northern hemi- 

 sphere. Trees or shrubs, with alternate leaves which are 

 simple in the common species but compound in P. 

 heterophylla and rarely in some of the apple tribe. The 

 species are cultivated for their edible fruits and for 

 ornament. Apples and Pears are the leading species. 

 The species are mostly sma'l trees, bearing clusters of 

 showy white or blush flowers with the leaves or in 

 advance of them. They are natives of the northern 

 hemisphere, mostly of cool temperate parts, and the 

 greater part of them are hardy in the northern states. 

 They are of easy culture. ' The pear-like species may 

 be worked on Pear stocks, and the apple-like species on 

 Apple stocks. 



The fruit of Pyrus is of the kind known to botanists 

 as a pome. The morphology of the pome is still a sub- 

 ject of dispute, although most botanists now agree in 

 considering it to be a hollow torus (receptacle) in which 

 the ovary is imbedded. Fig. 2019 illustrates the theo- 

 retical structure. The ovary is at b, wholly inclosed in 



ity like an apple, the flesh bearing grit cells; styles 

 usually free or not united at the base. (Nos. 1-5.) 



Of these plants there are perhaps 15 to 20 species, 

 natives to south-central Europe and Asia, with the 

 greatest expansion in the Grecian -Asia Minor-Syrian 



2018. Flowers of apple. 

 The ovaries are shown in the section, an ovule being at O 



the fleshy torus a. Most of the edible part of the Apple 

 or Pear, therefore, is considered to be torus, whereas 

 the core is ovary. This ovary is of five carpels or cells, 

 as shown in the cross-section, Fig. 2020. It was formerly 

 held that the edible part is largely calyx-tube, but vari- 

 ous morphological considerations have inclined students 

 to regard it as stem rather than calyx. One of these 

 reasons is the fact that Apples sometimes bear a rudi- 

 mentary leaf (as in Fig. 2021), an organ 

 which is commonly borne only by stems. 

 There are the widest differences of 

 opinion as to the generic limits of this 

 group of plants. What is regarded by 

 Bentham & Hooker as one genus is re- 

 garded by. others as 10 or 12 genera (see, 

 for example, E. Koehne, "Die Gattung 

 der Pomaceen," Wissensch. Beil. zum 

 Program des Falk-Realgymnasiums, Ber- 

 lin, 1890). In the present work, some of 

 these species ( the" quinces ) are set off 

 as Cydonia, the medlar as Mespilus, 

 and the mountain^ashes, chokeberries 

 and their kin as Sorbus. This restricts 

 Pyrus to the pear-like and apple-like 

 species. 



1. PEARS. (Pyrophorum). Fruit either 

 with a conical base or possessing a cav- 



2019. 

 Diagram of a 



pome (pear). 



Showing the 

 torus part at a 

 and the ovary 

 part at b. 



2020. Section of a pome (apple). 



Showing the interior or ovary part and the exterior 



or torus part. 



region. Of this particular region, Bossier (Flora 

 Orientalis) reduces the species to eight, P. communis, 

 P. cordata, P. amygdaliformis, P. elceagri folia, P. 

 salici folia, P. Syriaca, P. Boveana, P. glabra. Some 

 of these have fruits of comestible value, and it is not 

 impossible that they may be worthy of amelioration. 

 The best horticultural account of the species of Pears, 

 with particular reference to their pomological values, 

 will be found in vol. 1 of Decaisne's Le Jardin 

 Fruitier du Museum," where superb plates are given. 

 2. APPLES (Mains). Fruit with a sunken base or 

 "cavity," the flesh without grit cells; styles more 

 or less united below (Nos. 6-19). 



There are probably 20 good species of this sub- 

 genus, of wide distribution. The common Apple, 

 P. Mains, is probablylndigenous in southwestern 

 Asia. In Siberia, China and Japan, several spe- 

 cies are native, of which the best known are the 

 smooth-growing Crab trees with small fruits that 

 shed their calices. In North America is another 

 set, represented by the Garland Crab, P. coro- 

 naria of the East, the Narrow-leaved Crab, P. 

 angustifolia of the Southeast, the Prairie States 

 Crab, P. loensis, and the far western Crab, P. 

 fusca. It is difficult to find good characters to 

 separate the small-fruited Apples, particularly 

 the Asiatic forms. Carriere attempted to solve 

 thedifficulty (Pommiersmicrocarpes, Paris, 1883) 

 by referring them all to one polymorphous species- 

 group, Mains microcarpa. Although Pyrus and Malus 

 are very closely related botanically, they hold their dis- 

 tinctions with much persistency and they do not inter- 

 hybridize. Many writers prefer to keep the genera dis- 

 tinct, but the characters of separation are too minute 

 and technical for ordinary di- 

 agnostic purposes. It does not 

 follow that characters have 

 generic value merely because 

 they are constant. The marks 

 that separate Malus from Py- 

 rus are not readily determin- 

 able on the herbarium sheet, 

 and are therefore of relatively 

 little value to the systematist, 

 for whom generic lines are 

 chiefly erected. Their distinct- 

 ness is further shown by their 

 relations to inter-grafting, al- 

 though the graf tage-relation is 

 not coincident with the classi- 

 fication-relation. It is usually 

 impossible to graft the pear - species on the apple- 

 species with any degree of success; yet pears thrive on 

 quinces and also on hawthorns, which are well marked 

 genera. 



2021. A pome bearing a 

 rudimentary leaf (at A). 



