Page:EB1911 - Volume 23.djvu/763

Rh succulent torus, which in the other genera is dry. In Geum (avens) and Dryas (an arctic and alpine genus) the style is persistent In the After Wossidlo, from Strasburger's Lehrbuch der Botanik, by permission of Gustav Fischer.

2.—Pyrus communis (pear). 1, flowering branch; 2, a flower cut through longitudinally; 3, longitudinal section of fruit; 4, floral diagram.

fruit, forming a feathery appendage (Dryas) or a barbed awn (avens), either of which is of service in distributing the fruit. The Potentilleae are chiefly north temperate, arctic and alpine plants.

After Wossidlo, from Strasburger's Lehrbuch der Botanik, by permission of Gustav Fischer.

. 3.—Rubus fruticosus (blackberry). flowering branch; 2, longitudinal section of a flower; 3, fruit; 4, floral diagram.

The Roseae comprise the large genus Rosa, characterized by a more or less urn-shaped torus (fig. 4) enclosing the numerous carpels which form dry one-seeded fruits enveloped in the bright coloured fleshy torus. The numerous stamens surround the mouth of the torus. The plants are shrubs bearing prickles on the stems and leaves; many species have a scrambling habit resembling the brambles. The species of Rosa, like those of Rubus, are extremely variable, and a great number of subspecies, varieties and forms have been described. The Sanguisorbeae are a reduced form of Rosoideae. The dry one-seeded fruit is enclosed in the urn-shaped torus, which, however, is dry and inconspicuous, and the number of carpels is much reduced, sometimes to one (figs. 2, 5, 6). Petals are

After Duchartre, from Strasburger's Lehrbuch der Botanik, by permission of Gustav Fischer.

. 4.—Fruit of Rose, consisting of the fleshy hollowed axis, s′, the persistent sepals s, and the carpels fr. The stamens e have withered.

often wanting, as in Alchemilla (lady's mantle) and Poterium, and the flowers are often unisexual and frequently wind-pollinated, as in salad burnet (Poterium Sanguisorba), where the small flowers are crowded in heads, the upper pistillate, with protruding feathery stigmas, and the lower staminate (or bisexual), with exserted stamens. Agrimonia (agrimony) has a long spike of small honey less flowers with yellbw petals; in the fruit the torus becomes hard and crowned by hooked bristles which ensure the distribution of the enclosed achenes.

''Suborder IV. Neuradoideae'' contains only two genera of desert-inhabiting herbs with yellow flowers; and the five to ten carpels are united together and with the base of the cup-shaped torus, which enlarges to form a dry covering round the one-seeded fruits.

Suborder V. Prunoideae (fig. 7) is characterized by a free solitary carpel with a terminal style and two pendulous ovules, and the fruit a one-seeded drupe. The torus forms a cup from the edge of which spring the five sepals, five alternating petals and the ten to indefinite stamens. The plants are deciduous or evergreen trees or shrubs with simple leaves, often

with small caducous stipules, and racemes or umbels of generally showy, white or pink flowers. There are five genera, the chief of which is Prunus, to which belong the plum (Prunus communis), with several well-marked subspecies—P. spinosa (sloe or blackthorn), P. insititia (bullace), P. domestica wild plum), the almond (P. Amygdalus), with the nearly allied peach (P. persica), cherry (P. Cerasus), bird cherry (P. Padus) and cherry

After Wossidlo from Strasburger's Lehrbuch der Botanik, by permission of Gustav Fischer.

. 7.—Prunus Cerasus. 1, flowering branch: 2, a flower cut through longitudinally; 3, fruit in longitudinal section.

laurel (P. Laurocerasus). The tribe is distributed through the north temperate zone, passing into the tropics.

Suborder VI. Chrysobalanoideae resembles the last in having a single free carpel and the fruit a drupe, but differs in having the style basal, not terminal, and the ovules ascending, not pendulous; the flowers are also frequently zygomorphic. The 12 genera are tropical evergreen trees or shrubs, the great majority being South American. The zygomorphic flowers indicate an affinity with the closely allied order Leguminosae.