Abstract: Qinghai Lake is situated in north-west China, covering an area of 4635 km2 (36°32′—37°15′N., 99°36′—100°47′E.) at an altitude of about 3300 m. This brackish water lake is the biggest inland water in China, of which the salt content is about 14.383 g/l. Its, macrophytes, however, are still rarely known. This report is based on a collection by the auther in 1982. All Potamogetonaceae plants found in this lake are enumerated and keys to genera and species are provided. Altogether 7 new species belonging to Potamogeton and Zannichellia are described. They are as follows:1. Potamogeton miniatus Y. D. Chen sp. nov. (Fig. Ⅰ: 1)Herba submersa. Rhizoma elongatum, repens, ca 1 mm diam.. Caulis teres, 30—70 cm longus, 0.7—1 mm diam.. Folia atrovirentia, anguste linearia depressa, 5—7 cm longa, 0.5—1 mm lata, apice acuminata, stipulae vaginales 1.5—2 mm longae, apice libero membranaceo ca 5 mm longo. Pedunculi graciles 15—25 cm longi, miniati; spicae interruptae floribus 3—6 jugis praeditae; bracteae membranaceae, 1.5 mm longae, ca 3 mm latae margine undulatae vel lobatae; pedicelli longi, miniati; tepalum subrotundatum ca 2 mm diam. margine integrum; filamenta basi connata. Fructus subcompressi, oblique obovati vel subrotundati 2.5—3 mm longi, 2 mm lati, dorso rotundati ventre convexo, apice mucrone brevissimo instructi.Species nova affinis P. pectinato L. sed pedicello longo, miniato, filamentis basi connatis, fructu ventro convexo differt.Qinghai Lake alt. 3300 m, submerged, Aug. 28 1982, Y. D, Chen et R. S. Ni 415 (Typus PE), 408,417,419.2. Potamogeton erhaiensis Y. D. Chen sp. nov. (Fig. Ⅰ: 2)Herba submersa. Statura pro genera gracili. Caulis flavidus vel pallide flavovirens, filiformis ca 30—40 cm longus, ca 0.3 mm diam., internodiis 2—3 cm longis. Folia virella, tenuia depressa 4—6 cm longa ca 0.2 mm lata, apice acuminata uninervia; stipulae vaginales ca 2 cm longae, apice libero ca 4 mm longo membranaceo. Pedunculi ca 5—8 cm longi, caule crassioes; spicae interruptae fioribus 4—5 jugis praeditae; bracteae membranaceae, fete delteae, ca 1.5 mm longae, 2 mm latae, margine lobatae; tepalum plus minus clypeatum ca. 1.5 mm diam. filamenta basi connati, discoidei, stigmata subrotundata. Fructus subcompressi, dorso rotundati, ventre convexi, apice breviter rostrati.Species nova P. miniato Y. D. Chen affinis, a quo differt planta multo minore, pedunculo caule crassiore, tepalo minore plus minus clypeato, stigmate subrotundate.Qinghai: Erhai Lake alt. 3300 m, submerged, Aug. 29 1982, Y. D. Chen et R. S. Ni 451 (Typus PE).3. Potamogeton applanatus Y. D. Chen sp. nov. (Fig. Ⅰ: 3)Herba submersa. Caulis in sicco compressis, flavidus vel pallide flavovirens, 30—40 cm longus, ca 1 mm . diam., raro ramifer, internodiis 3—4 cm longis. Folia viridia 4—6 cm longa, ca 0.2—0.5 mm lata, apice acuminata, 1-nervia; stipulae vaginales 1.2 cm longae, apice libero 7 mm longo, membranaceo. Pedunculi 5—8 cm longi teretes; spicae interruptae, floribus 3—4 jugis praeditae; bracteae membranaceae, 1.5 mm longae, 2.5 mm latae, margine lobatae; tepalum rotundatum ca 2 mm diam., margine membranaceum; anthera ca 0.7 mm longa; filamenta brevissimi. Fructus subcompressi, 3—3.5 mm, longi, 2—2.5 mm lati, apice mucrone obliquo brevi instructus, dorso et ventre carinato-convexi.Species nova P. miniato proximus, sed caule in sicco compresso, raro ramifero, vagino clauso, tepalo margine membranaceo, fructu dorso ventreque carinato-convexo bene differt.Qinghai Lake, alt. 3300m, submerged Aug. 27 1982 Y. D. Chen et R. S. Ni 400 (Typus PE)4. Potamogeton bracteatus Y. D. Chen sp. nov. (Fig. Ⅰ: 4)Herba submersa, Rhizoma brevis aggregatum. Caulis gracilis ca 0.5 mm diam., 30—40 cm longus. Folia atrovirentia, filiformia, 3—5 cm longa, ca 0.3 mm lata, parte superiore saepe curva, apice acuminata; stipulae vaginales 10—15 mm longae, apice libero membranaceo, ca 5 mm longo, Pedunculi 7—10 cm longi; spicae interruptae, floribus 3—4 jugis praeditae; bracteae membranaceae, fere flabellatae ca 1 mm longae margine undulatae vel lobatae; tepalum subrotundatum val flabellatum ca 2.5mm latum margine membranaceum, medio crassiusculum. Fructus subcompressi, oblique obovati, 3—4 mm longi, ca 2 mm lati, apice breviter rostrati, ventre plani dorso rotundati.Species nova P. miniato similis, a quo differt rhizomate cauleque gracili, foliis in parte superiore saepe curvis, tepalo margine membranaceo medio crassiusculo.Qinghai Lake alt. 3300m, submerged Aug. 28 1982, Y. D. Chen et R. S. Ni 427 (Typus PE) 4325. Potamogeton leptanthus Y. D. Chen sp. nov. (Fig. Ⅱ: 1)Herba submersa. Caulis ramosissimus, 10—15 cm. longus, internodiis superioribus ca 0.5—1 cm longis. Folia filiformia 5—8 cm longa, ca 0.5mm lata, uninervia, stipulae vaginales margine scariosae, apice libero 5 mm longo, spicae breves floribus 3—4-jugis praeditae; bracteae membranaceae, 0.5—1 mm longae apiculatae; tepalum fere reniforme 2.2 mm longum ca 1.2 mm latum; anthera subrotundata ca 1 mm longa; filamenta basi liberi, 0.5—1mm longi. Fructus ca 2 mm longi, 1.5 mm lati, subcompressi obique obovati.Proximus P. bracteato Y. D. Chen, Sed vagina clausa, floribus brevioribus, bracteis apice apiculatis, connectvis basi liberis distinctus.Qinghai Lake, alt. 3300m, submerged Aug. 28 1982, Y. D. Chen et R. S. Ni 418 (Typus PE) 420, 440.6. Potamogeton nanus Y. D. Chen sp. nov. (Fig. Ⅱ: 2)Herba submersai; rhizoma brevis vel obscurum. Caulis filiformis, caespitosus, flavidus vel pallide flavovirens, ca 4—6 cm longus, ca 0.5 mm diam. internodiis 0.5—1.5 cm longis. Folia atrovirentia, linearia, in sectione transversali triquetra vel semilunata apice acuminata, 1-nervia; stipulae vaginales 1 cm longae, apice libero ca 4 mm longo, membranaceo. Pedunculi 2—3 (-5) cm longi; spicae interruptae floribus 4-jugis praeditae; bracteae membranaceae, 1—1.5 mm longae, 1.5—2.5 mm latae, margine lobatae; tepalum rotundatum ca 1—1.5 mm diam.; connectivi inaequilongi, basi connati. Fructus compressi oblique obovati.Species nova P. leptantho affinis, sed caule caespitoso, breviore 4—6 cm longo, rhizomate brevi vel obscuro, tepalo rotundato bene differt.Qinghai Lake, alt. 3300m submerged Aug. 27 1982, Y. D. Chen et R. S. Ni 406 (Typus PE), 425, 4287. Zannichellia qinghaiensis Y. D. Chen sp. nov. (Fig. Ⅱ:3)Herba submersa. Caulis filiformis, purpureofuscus, 4—10 cm longus, vel ultra. Folia filiformia, 1.2—2 cm longa, ca 0.5 mm lata, 1-nervia apice acuminata, basi evaginata. Flores axillares; carpella 4(-5) in pedicello brevi in umbellam disposita. Fructus saepius reniformes vel semilunati, ca 2 mm longi 1 mm lati, apice rostrati, rostro ca 2 mm longo, dorso et ventre convexo, breviter pedicellati, vel sine.Species nova Z. palustri L. affinis, sed planta minore, gracili, caule purpurcofusco, fructus rostro aequilongo diversa. (注:中文序号第9种)Qinghai Lake alt. 3245m, submerged Sep. 3 1982, Y. D. Chen et R. S. Ni 442 (Typus PE)