(b. Autun, France, 16 March 1812; d. Lille, France, 1892)
After military service as assistant surgeon in Maubeuge and Strasbourg (1836-1838) and as surgeon and pharmacist in Algeria (1839-1844), Garreau became professor of natural history at the University of Lille in 1844. His earliest researches dealt with the relative values of both surfaces of a leaf as sites of gaseous exchange, especially the exhalation of water vapor. He measured the amount of water excreted by placing small glass domes, containing a waterabsorbing substance, on opposite sides of a leaf and found no direct correlation between the amount of evaporation and the number, of stomata. He concluded that the epidermis determines transpiration, the cuticular layer being very important. On the veins, where transpiration was the most intensive, he found almost no cuticle.
Garreau also confirmed that leaves are able to absorb water, as Bonnet had proposed in 1754, and determined the osmotic properties of the epidermis and cuticle. Here he observed a more direct correlation between the exhalation of carbon dioxide and the number of stomata. Garreau discovered that there was no relation between the cuticle and the cells of the epidermis (1850). The cuticle already exists before differentiation of the epidermal cells occurs. He thought that the cuticle was a living tissue and that the younger the organ producing the cuticle, the stronger its osmotic activity.
Garreau also worked on the theory of respiration and nutrition of green plants, proposed by Ingen-Housz in 1779; In 1851 he confirmed the results of the work of H. B. de Saussure, who had shown that the great mass of the vegetable body is derived from the carbon dioxide of the atmosphere and the constituents of water. Garreau observed that reduction of carbon dioxide, which he called the nutritive function, was dependent on light and was independent of respiration. Although not strictly separating the effects of assimilation and respiration. Garreau protested against distinguishing a “diurnal” and a “nocturnal” respiration in green plants.
Further, Garreau showed that there was a direct relation between respiration and heat production. The idea of a vital force within the plant body was deprived of one of its chief supports when it was recognized that the natural heat of organisms is the result of chemical processes induced by respiration. Garreau explained the high intensity of this phenomenon in Arum inflorescences by showing that the surface area is large in relation to volume.
Garreau married in 1846; he had four children. He was an officer of the Académie des Sciences and the Legion of Honor. In 1862 he became a member of the Institut Impérial des Sciences.
I. Original Works. Garreau’s works include “(Sur la nature de la cuticule, ses relations avec l’ovule,” in Annales des sciences naturelles (Botanique), 3rd ser., 13 (1850), 304-315; “Recherches sur l’absorption et l’exhalation des surfaces aériennes, des plantes,” ibid., 321-346; “De la respiration chez les plantes,” ibid., 15 (1851), 5-36; “Mémoire sur les relations qui existent entre l’oxygène consommé par le spadice de l’Arum Italicum en état de paroxysme, et la chaleur qui se produit,” ibid., 250-256; “Nouvelles recherches sur la respiration des plantes,” ibid., 16 (1852), 271-292; “Mémoire sur la formation des stomates dans l’épiderme des feuilles de l’éphémère des jardins, et sur l’évolution des cellules qui les avoisinent,” ibid., 4th ser., 1 (1854), 213-219; “Recherches sur les formations cellulaires, l’accroissement et l’exfoliation des extrémités radiculaires et fibrillaires des plantes,” ibid., 10 (1858), 181-192, written with Brauwers; Recherches expéerimentales: 1° sur les causes qui concourrent à la distribution des matières minérales fixes dans les divers organes des plantes,” in Annales des sciences naturelles, 13 (1860), 145-218; and “Mémoire sur la composition élémentaire des faisceaux fibro-vasculaires des fougères,” in Comptes rendus hebdomadaires des sèances de l’Académie des sciences, 50 (1860), 854-855.
II. Secondary Liteature. Short descriptions of Garreau’s work are to be found in M. Duchartre, Rapport sur Ie progrès de la botanique physiologique (Paris, 1868). An obituary notice appeared in Journal de pharmacie et de chimie, 5th ser., 28 (1893), 109.
A. P. M. Sanders.