222 J. O. HAGSTRÖM, CR1TICAL RESEARCHES ON THE TOTAMOGETONS. 



convinced that the forms in question are a hybrid plant, which, like P. Zizii, in sonie 

 crosses is able to produce some fruit or other. For the distribution and the subsist- 

 ence of the plant, however, this faculty, no doubt, plays a very subordinate part. 

 What I have said above of P. Zizii is true about P. /litens also. The list below displays 

 its abundant occurrence in the Scandinavian peninsula, b ut there is no independent 

 species P. nitens there and I have seen no such a plant from any other place either. 



By cooperation of P. perfoliatus with cordate clasping leaf-base and gramineus, 

 the submersed leaves of which are lanceolate, the base of those leaves of the bastard 

 usually grows rounded-cordate, half clasping. Most rarely wc meet with forms, the 

 stem-leaves of which present a lanceolate base, in which case the branch-leaves, 

 nevertheless, have a more or less rounded base. In doubtful cases the nitens- and 

 g ra mineus-ior ms are distinguished by the bases of the branch-leaves. The apex of 

 the submersed leaves is in general cuspidate, extremely seldom rounded. In the 

 former case often sharp as in P. gramineus, but often a little broader (influence from 

 P. perfoliatus), in perfect analogy with the hybrids P. deeipiens and Babingtonii. 

 The upper leaves of the spike-region turn usually, by cooperation of the two species, 

 short and broadly petioled with sloping lamina. When gramineus in this part predo- 

 minates the petiolcs grow longer, ncarly so long as in P. gramineus, but always a 

 little broader especially upward. If P. perfoliatus, again, has gained aseendency, these 

 leaves also turn sessile with the base half clasping or ovate-lanceolate. As regards 

 the consistency and strueture, the top-leaves are an intermediate thing between 

 f loating leaves and submersed leaves, typically furnished with numerous stomaia 

 (influence from P. gramineus). As the difference between the effioienta is most 

 evident in the spike-region, the hybrid forms also grow most different there, and 

 consequently I have tried to group the numerous forms of the hybrid aeeording to 

 those conditions. Cf. O. Hagström in Nkuman, Sveriges Flora 11)01, 707! This 

 is so much the rather suitable, as the hybrid, like the parents, gcnerally in an earlv 

 state produces spikes, whercupon it prolongs itself by branches of as far as the fifth 

 rank or more, by which a great abundance of spikes exists and consequently plenty 

 of involucral leaves mostly are present. The submersed leaves are always 

 endowed with small, most frequently very fugacious denticles. Nerve-spaces usually 

 more elongated than in P. gramineus (influence from P. perfol.). Ligules decaying 

 sooner than in P. gramineus, likewise an influence from the other parent-species. 

 From the same causc the pedunelcs are typically shortcr than in /'. gramineus, but 

 often a little thickened at the middle or upwards. The Bpikes of fche speeimens qow 

 examined are to the greatest part quite sterile. Aeeording to our experienee fruiting 

 nitens, of which so much is spöken, is extremely rare, but in different eolleetious, 

 true enough, 1 have now and t lien met with fruiting speeimens determined as /'. 

 nitens, which in reality have been pure P. gramineus. 



As regards t 1k^ stem-anatomy you will always lind oue or two cortioal cncles 

 of vasoular and bast bundles beside the subepidermal strands. The endodermis-cells 

 and the diagram of the stele vary from pure, oblong granlin* us-\\\)v to pure t rio-t \ pr 

 of /'. perfoliatus, hut an amalgamation of both, a hybrid-diagram, is the commonest. 



