Orobanchaceae
S.M.H. Jafri
Herbarium, Karachi University, Karachi.
Herbaceous root-parasites, devoid of chlorophyll, scapigerous, often fleshy and covered with scale-leaves only. Inflorescence in racemes or spikes, rarely 1-flowered. Bracts scaly, ± like the scale-leaves; bracteoles present or absent, 2, much narrower than bracts, usually free, rarely slightly to conspicuously connate with calyx-tube. Flowers hermaphrodite, hypogynous, zygomorphic, blue, violet, yellowish to brown. Calyx 2-4 (-5)-lobed or toothed, sometimes evidently 2-segmented, rarely spathaceous, persistent, scaly. Corolla often bilabiate, lobes subequal to unequal. Stamens 4, epipetalous, in 2 subequal pairs, anthers mostly connivent; filaments filiform, often hairy at the base, included, rarely subexserted; anthers 2-celled (rarely 1 cell imperfect and spurred). Ovary superior, 2(-3)-carpellary, syncarpous, 1 (-2)-locular, with numerous ovules on (2-)4(-6) parietal placentae; style simple, often long with curved tip and ± 2-lobed, capitate stigma. Fruit an ovoid to oblong capsule, 1-celled, dehiscing into 2 incompletely separating valves, glabrous, usually many-seeded; seeds very small, endospermous with minute, undifferentiated embryos.
About 14 genera and nearly 200 species, chiefly of the warm temperate zones of the Old World; represented in Pakistan by 4 genera and c. 22 species.
The family is very closely allied to Scrophulariaceae, but the ovary is 1-locular and the plants are without an underground elongated rootstock (except tuber) or true roots (this, with some other characters, leaves Lathraea in Scrophulariaceae but is sometimes included in Orobanchaceae). Aeginetiaceae (Livera in Ann. Roy. Bot. Gard. Peradeniya 10(2):1.159.1927), which was separated from Orobanchaceae on account of subequally 5-lobed corolla, spathaceous calyx etc., does not justify its separate identity.
The family seems to be under-collected in our area and specimens often lack field notes on underground parts, flower shape and colour, so essential for correct identification. In herbarium specimens, the flowers become brittle and their colour fades.
Acknowledgements: We are grateful to the United States Department of Agriculture for financing this research under P.L. 480. Thanks are also due to Messrs. B.L. Burtt, I.C. Hedge and Miss J. Lamond of the Royal Botanic Garden, Edinburgh, for going through the manuscript and giving valuable suggestions.
