Sagittaria pygmaea Miq. (Japanese epithet: Urikawa) is a wild plant of the Alismataceae growing in paddy fields of Japan. The plants were collected in Fukui Prefecture between late June and early July. In the acid hydrolysate of the whole plant, diaminopimelic acid and an unknown amino acid were found, besides the usual amino acids. The unknown amino acid showed an almost indistinguishable retention time to that of methionine or diaminopimelic acid under the usual conditions of amino acid analysis. Its ¹H NMR spectrum was similar to that of lysine except for the additive presence of a singlet for 2H at δ 4.06 which can be assigned to N-α,-CO function. Moreover, the signals of δ 4.21 in ¹H NMR and δ 54.5 in ¹³C NMR indicated the α-amino acid structure, N-CHR-COOH. Furthermore, from its ¹³C NMR, it was revealed that 5 × CH₂, 1 × CH, and 2 × CO carbons are present in the molecule. The neutral behaviour on paper electrophoresis and the elemental analysis indicated the presence of two NH₂ (or NH) groups and two COOH groups. Thus a tentative structure was deduced; either Nε-carboxymethyl(CM)-Lysine (1) or Nα-CM-lysine (2). In order to confirm the structure, both amino acids were then synthesized starting from L-lysine according to the procedures shown in the Experimental. By comparison with the two synthetic compounds thus obtained, the natural amino acid was found to be identical with Nε-CM-L-lysine (1) and different from Nα-CM-derivative (2) in respect of TLC, amino acid analysis, ¹H NMR and [α]D. This is a first finding of Nε-CM-L-lysine in plants, although its occurrence as a free amino acid in human urine has been recently reported [1]. The amino acid was never found as a free form in the plant, but only in the hydrolysate. This may mean that the enzymical carboxymethylation may occur at the ε-NH₂ group of the lysine residue in a conjugated form. Since nothing is known about the biosynthetic formation of this amino acid, the possibility of its artificial formation by means of either a herbicide or a pesticide supplied to the paddy field cannot be excluded. Mucilage commonly occurs in higher plants [1, 2] but, so far, this class of natural products has not received any attention by workers studying plant cell cultures. Since mucilage finds wide industrial application [3], it was considered worthwhile to investigate callus cultures of some medicinally and economically important plants for their mucilage contents and for the composition of constituent monosaccharides in the mucilage. The data presented in Table 1 indicate that callus cultures of higher plants are relatively rich in mucilage, which commonly makes up 8-10% of the dry wt. In callus cultures of Trigonella foenum-graecum 21.2 % mucilage is found. The seeds and 3-week-old seedlings of Trigonella foenum-graecum contain 26.3 and 10.8 % mucilage, respectively. Galactose and mannose appear to be the common constituent monosaccharides in mucilage of callus cultures. In mucilage from cultures of Catharanthus roseus, glucose instead of galactose, is detected and in mucilage from Nicotiana glauca, only galactose is present. In the case of T. foenum-graecum and Glycine max, a striking similarity between the qualitative and quantitative composition of mucilage in callus cultures (Table 1) and mucilage in organs of the intact plant [4, 5] is observed.