258 JOURNAL OF THE ARNOLD ARBORETUM [VOL. XXXIV STUDIES IN THE BORAGINACEAE, XXV A REVALUATION OF SOME GENERA OF THE LITHOSPERMEAE IVAN M. JOHNSTONAs A BACKGROUND for a study of Lithospermum and its immediate relativesit has been necessary to investigate and determine the characters of someof the other genera included in the Lithospermeae. It has been surprisingto discover that most of these latter genera have a variety of interestingfeatures that have gone unmentioned in published accounts of them. Somuch of interest was found that it has seemed desirable to prepare newand more complete descriptions of these genera and also to discuss theircharacters and relations. Six genera, all confined to the Old World, areso treated in the present paper. The general affinities of the genera treated are well indicated by theirpollen morphology. Lithodora appears to be a highly specialized derivativeof the Lithospermum-complex, notable chiefly for its frutescent habit andaberrant nutlets. Its pollen has eight pores and a form duplicated also inLithospermum and its close allies. The remaining five genera discussedappear to be more closely related to one another than to Lithospermumor its close allies. Except in one section of Moltkia their pollen is 3-poredand hence of a type different from that in Lithospermum and its immediateallies. As a group the five genera are also notable for the frequent develop-ment of bent nutlets and for the recurring manifestations of bilateral sym-metry in their corolla and androecium. The six genera discussed may be distinguished by the following key:Nutlets circumscissile above the base, their major seminiferous portion falling away, leaving the true base persisting as a usually cupulate appendage permanently affixed to the gynobase; corolla without annulus or appendages; pollen ellipsoidal or somewhat ovoid, pores usually 8, borne at or slightly below the middle of the grain; body of nutlet straight. ........ .. .. 1. Lithodora.Nutlets detaching completely from the gynobase. Corolla without annulus; stamens all affixed at the same height on the corolla; pollen globose or globose-ellipsoid, pores 3-8, equatorial; body of nutlet somewhat bent. Corolla without appendages; lobes short, broadly imbricate in the bud, becoming erect; style exserted only after the corolla is fully developed; anthers not ciliate; pollen with 3-8 pores. ... .. 2. Ml oltkia. Corolla with squamate appendages between the base of the filaments; corolla-lobes elongate, very narrowly imbricate in the bud; style precociously exserted, protruding from the incom-pletely developed corolla; anthers having the margins of the theca ciliate with crowded stout hairs; pollen with 3 pores. .................. . ......... . 3. H alacsya.