Over enige kritische planten van onze Flora

1. Alisma repens has been described by Lamarck. A detailed description of it and a good figure are to be found in Cavanilles [Icon. I (1791) n. 61, t. 55]. The latter does not mention, however, that the flowers are larger than in A. ranunculoides L. and that the fruits are smaller and covered with glandular warts. When the genus Echinodorus Rich, is to be distinguished, A. repers. has to be transferred to it. In Central European literature (cf. A.-G. Synopsis) the plant which in our opinion is specifically different from E. ranunculoides (L.) Engelm., has been treated as a variety of this species or merely (e.g. by Buchenau, the monographer of Alismataceae) as a modification without systematic value. It seems that this mediterranean-atlantic species is not well known in Central Europe and that it has been confounded with slender forms of E. ranunculoides. E. ranunculoides occurs all over the Netherlands in suitable localities, whereas E. repens is only known from the „Kempense” district, [cf. Van Soest in Heukels, Geill. Schoolfl., 13. ed. (1949) p. 8], 2. Potamogeton fluitans Roth has been repeatedly mentioned for the Netherlands, but all specimens concerned belonged to P. oblongus Viv., perhaps with the exception of a plant from Zalt-Bommel, collected by van Spijck Vermeulen, of which the specimens have been lost. Genuine P. fluitans has been collected recently by the present authors and by the late Joh. Jansen in several places in the river Waal. The plants rarely flower and hardly fruit, which is often the case in Central Europe too, although Schinz & Keller and others assert the contrary for Switzerland. It seems improbable that P. fluitans should be a hybrid of P. natans and P. lucens, as these species were never found by the authors in the localities of P. fluitans. Moreover they looked in vain for P. fluitans in those places where P. natans and P. lucens occur together. 3. Sedum Telephium L. ssp. purpureum (Schult.) Sch. et K. is not rare in the Netherlands. The ssp. maximum (Hoffm.) Rouy et Camus, which could be expected for phytogeographical reasons had, up to the present, not been found in this country. The authors discovered typical ssp. maximum in great numbers in the Millingerwaard and less typical specimens in a few localities around Nijmegen. A rich locality of ssp. Fabaria (Koch) Sch. et K. was discovered by the late Joh. Jansen near Grave (prov. Noord-Brabant). 4. A species of Mimulus, mentioned in Dutch botanical literature as M. luteus L. (native of S. America), appeared to be the North American M. guttatus DC., at least as to the specimens growing along the river Waal. This agrees with the occurrence of the latter species along riverbanks in Germany.