162 



J. O. HAGSTROM. CRITICAL RESEARCHES ON THE POTAMOGETOXS. 



nyp. two-(l-)layered, scattered subepidermal strands, no ligular or cauline bundles, 

 O-end., and a stele with a prototypic diagram. 



This species resembles very much some other South- American species, where- 

 fore I think it proper to give the following 



Synopsis of some S. American coriacious-leaved species, which non-fruiting often 

 are verv difficult to distinguish from each other: 



A. Pseudo-hypoderma wanting: 



a. Cortical strands entirely absent P. 



b. Ligular strands few, in one cirele » 



c. Lig. str. + cauline str., in two circles * 



B. Pseudo-hyp. one-layered: » 



C. Pseudo-hyp. t\vo-(l — 4-)layered. Central cyl. of the prototypic type: 



a. Cortical strands entirely absent P. apicalis. 



b. Subepidermal strands present » jerrugineus. 



c. Ligular bundles only » badioviridi*. 



d. Subepid. str. + lig. + cauline bundles » linguatus. 



Distribution of P. jerrugineus. Argentinc Rep., Casa Bamba, Sierra chiea do 

 Cordoba, 09, Stuckert, n. 19870 (hb. Hann.). Uruguay, Vegigas, 06, Bbrro, n. 

 4189 (hb. Haun.). 



nodosus. 

 montevidensis. 

 stenostacJu/s. 

 spoliatus m. 



P. linguatus Hagstr. 



Ap. P. Dusen, Zur Kenntnis der Gef.pfl. des siidl. Patagoniens, in Ofvcrsigt 

 af K. Vet. Ak. Pörh., 1901, no. 4, 259—262, cum fig. - Pig. 1, 7>\ 80. 



p ctr This species is at full development coarse-grown 



with thick and rigid stem, broad, manv-ncrved (±21 nerv.), 

 not lacunous submersed leaves, and broad, strong ligules. 

 The floating leaves seem generally not lo appear al fche 

 primary spike, but first in the eking piece of the slem, 

 which consists of manv internodes. The sliffness of the 

 stem is caused by the ratlicr short epidermis-cells, the 

 2 — 3-laveied pseudo-hvpoderma, (he numerous subepidermal 

 strands, and the many frce bundles of the stele. The 

 median bundles of the stele are tvpically four and the 

 lateral ones about eighf, four on eacb side, enconu.assed 



view, ','■ ' ''"' othei detaile I refer u< a ~> i 



the original deaoription, where alao a by an n-endodcrmis, the tthole thus prcsentillg a proto- 



typie aspect (Pig. 80, A). 

 The fruit and styles causc lliis species lo be united with the Amplifolii. The 

 styles are namely short and thick with oval or oblong small Btigmas. Pollen 

 spheric of middle size. /'. <il/>iiins forms a separate group on acoounl of the styles 



and liuits and so does also /'. nodo8U8 hecanse of llie leaf serrulat ion. The phylojjc- 



tr 

 Fig. hi). /'. lingualua Haostb. a, 

 Aiiatoui i.- diagram "t the central stele, 

 (;-, bnndle trio, '•>>■, opposite bnnd 



