Fruit cylindrical. Styles 5, rarely 3-4, opposite the sepals.--Species 20. Extra-tropical regions and mountains of the tropics. Some are used medicinally. =Cerastium= L. 28. Petals minutely toothed. Styles 3. Ovules numerous. Fruit cylindrical. Seeds peltate, compressed dorsally. Flowers in umbel-like cymes.--Species 1. North Africa. =Holosteum= L. Petals entire, slightly notched, or wanting. 29 29. Styles as many as the sepals, 4-5. 30 Styles fewer than the sepals, 2-4, very rarely 5. 32 30. Styles opposite the sepals. Stamens 8. Fruit opening at the top by 8 recurved teeth. Leaves lanceolate.--Species 1. North Africa. (Under _Cerastium_ L.) =Moenchia= Ehrh. Styles alternating with the sepals. Stamens 4, 5, or 10. Fruit opening to the base in 4-5 valves. 31 31. Stamens as many as and alternating with the sepals. Petals none.--Species 2. Subantarctic islands. =Colobanthus= Bartl. Stamens as many as and opposite the sepals, or twice as many. Leaves subulate.--Species 7. North Africa, high mountains of Central Africa and subantarctic islands. Some are used as ornamental plants. “Pearlwort.” =Sagina= L. 32. Styles 2. Ovules 2-4. Stamens 2-4. Sepals 4. Fruit opening to the base in 2 valves. Seeds 1-2. Leaves subulate.--Species 5. North-west Africa. =Buffonia= L. Styles 3-5, rarely 2, but then (as usually) ovules more than 4. Sepals nearly always 5. 33 33. Valves of the fruit entire, as many as styles.--Species 8. North Africa and northern East Africa. (Including _Minuartia_ L., under _Arenaria_ L.) Alsine Wahlenb. Valves of the fruit 2-toothed or 2-parted; in the latter case apparently twice as many as styles. 34 34. Seeds with an appendage at the hilum. Flowers white.--Species 2. North-west Africa. (Under _Arenaria_ L.) =Moehringia= L. Seeds without an appendage. Stamens 10.--Species 10. North Africa and northern Central Africa. “Sandwort.” =Arenaria= L. 35. (1.) Calyx with an odd number of ribs. Petals usually with contorted aestivation. Styles or stigmas 2. [Tribe DIANTHEAE.] 36 Calyx with an even number of ribs. Petals usually with quincuncially-imbricate aestivation. Styles or stigmas 3-5. [Tribe LYCHNIDEAE.] 41 36. Calyx with scarious stripes between the lobes and with 5-35 ribs. 37 Calyx without scarious stripes, with 15-55 ribs. 38 37. Seeds peltate; embryo nearly straight. Leaves linear.--Species 2. North Africa. (Including _Dianthella_ Clauson). =Tunica= Scop. Seeds reniform; embryo curved. Leaves lanceolate, oblong, elliptical, or ovate.--Species 2. North-east Africa to the Island of Socotra. The roots are used in medicine and as a substitute for soap. =Gypsophila= L. 38. Petals with scales at the base of the blade, which are sometimes reduced to hairs. Calyx not surrounded by bracts. 39 Petals without scales at the base of the blade, but usually with a winged claw. 40