[153] On growth in relation to light, see Davenport, Exp. Morphology, II, ch. xvii. In some cases (as in the roots of Peas), exposure to light seems to have no effect on growth; in other cases, as in diatoms (according to Whipple’s experiments, quoted by Davenport, II, p. 423), the effect of light on growth or multiplication is well-marked, measurable, and apparently capable of expression by a logarithmic formula. The discrepancy would seem to arise from the fact that, while light-energy always tends to be absorbed by the chlorophyll of the plant, converted into chemical energy, and stored in the shape of starch or other reserve materials, the actual rate of growth depends on the rate at which these reserves are drawn on: and this is another matter, in which light-energy is no longer directly concerned.
[154] Cf. for instance, Nägeli’s classical account of the effect of change of habitat on Alpine and other plants: Sitzungsber. Baier. Akad. Wiss. 1865, pp. 228–284.
[155] Cf. Blackman, F. F., Presidential Address in Botany, Brit. Ass. Dublin, 1908. The fact was first enunciated by Baudrimont and St Ange, Recherches sur le développement du fœtus, Mém. Acad. Sci. XI, p. 469, 1851.
[156] Cf. Loeb, Untersuchungen zur physiol. Morphologie der Thiere, 1892; also Experiments on Cleavage, J. of Morph. VII, p. 253, 1892; Zusammenstellung der Ergebnisse einiger Arbeiten über die Dynamik des thierischen Wachsthum, Arch. f. Entw. Mech. XV, 1902–3, p. 669; Davenport, On the Rôle of Water in Growth, Boston Soc. N. H. 1897; Ida H. Hyde, Am. J. of Physiol. XII, 1905, p. 241, etc.
[157] Pflüger’s Archiv, LV, 1893.
[158] Beiträge zur Kenntniss der Wachstumsvorgänge bei Amphibienembryonen, Bull. Acad. Sci. de Cracovie, 1908, p. 783; cf. Arch. f. Entw. Mech. XXVIII, p. 160, 1909; XXXIV, p. 489, 1912.
[159] Fehling, H., Arch. für Gynaekologie, XI, 1877; cf. Morgan, Experimental Zoology, p. 240, 1907.
[160] Höber, R., Bedeutung der Theorie der Lösungen für Physiologie und Medizin, Biol. Centralbl. XIX, 1899; cf. pp. 272–274.
[161] Schmankewitsch has made other interesting observations on change of size and form, after some generations, in relation to change of density; e.g. in the flagellate infusorian Anisonema acinus, Bütschli (Z. f. w. Z. XXIX, p. 429, 1877).
[162] These “Fezzan-worms,” when first described, were supposed to be “insects’ eggs”; cf. Humboldt, Personal Narrative, VI, i, 8, note; Kirby and Spence, Letter X.