Germination, Maturation, and the Role of External Factors

Zoology also inspired the Academy's experiments and theories about germination. Perrault recommended microscopic research to discover just how plants grew from seeds, and Dodart compared the Academy's studies of germination to studies of chicks in the egg.^[19] Although academicians never rivaled the detail of Grew's or even Samuel Foley's studies of the anatomy or development of germinating seeds,^[20] they claimed interesting analogies between plant and animal parts. Working with a germinating white bean squash and other seeds, Mariotte and Perrault described the filament connecting lobes to leaves as an umbilical cord. Mariotte also thought that seed lobes of beans, pumpkins, cucumbers, and melons resembled the yolk of an egg or the liver in being a source of food for the embryo plants.^[21]

Mariotte explained the process of germination mechanically:

It is thus probable that the principal parts of the germination of Plants are contained in their seeds, and that they are predisposed to form fibers and pores suitable for the filtration and the union of certain principles that pass there, as

if through channels or molds; from which the other parts are formed, such as fruits, seeds, and the beginnings of the second germination.^[22]

His mechanistic and analogical explanation challenged traditional views of savants like Duclos. Where Mariotte dismissed a vegetative soul in plants on the ground that no one had ever found one, Duclos preferred vegetative souls to analogies between the parts of plants and the organs of animals. Duclos thought plants and soil had similar natures; unlike his colleagues he did not differentiate the various parts of plants by their function, saying rather that all parts of plants (and of soils) contributed equally to germination and maturation.^[23]

Any account of germination had to weigh the roles of the plant itself and of external conditions such as sun, soil, air, and water. Perrault and Mariotte stressed the sun. Perrault conjectured that it cooked nutritious minerals in the rainwater. Mariotte demonstrated that sunlight was essential to the growth of plants by comparing seedlings grown under earthenware pots with seedlings grown under glass domes. He proposed two theories, one mechanical, the other chemical, to explain the sun's effect: either sunlight encouraged water to rise in the plant, and then water turned the plant green, or sunlight affected the chemical nutrients in the water.^[24]

Soil, air, and water seemed to be the most influential external conditions for germination and maturation. Local conditions could encourage or inhibit growth, and plants either depended passively on what they took from the soil or transformed it to suit their needs. Mariotte and Perrault discussed the nutrients plants required from the soil. Tournefort thought that the earth's juices were the single most important stimulus of germination. They were prepared in the soil by agitation, moisture, heat, or cold, and shaped by the air and the pores of soil through which they passed.^[25] Tournefort emphasized mechanical processes — motion, air pressure, the sieving effect of pores — but he also considered the chemical composition of soils.^[26]

Academicians studied earths systematically in the 1670s. In 1675 Dodart proposed several experiments. He planned to extract "the salts, and if possible, some other substances from the different kinds of earths." He hoped to distinguish soils chemically, to differentiate among the salts in soils, to discover a connection between salts found in the earth and the salts of plants that grew there, and to identify the different proportions of salts in the same soil under various conditions.^[27]

For Dodart and Borelly the purpose of research on earths was to understand what made soil fertile. But they could not persuade Bourdelin

to study soils according to the methods they preferred. From the end of 1675 until the end of 1677, Bourdelin analyzed marls, clays, and other kinds of soils, distilling them as usual in the retort, some with and others without the fixed salt of saltpeter. He calcinated the testes-mortes and then tested the liquids extracted for their reactions to chemical solutions, just as he did with the products of distilled plants. Bourdelin found that earths released liquid with a sulphurous odor, vitriolated salts, volatile salt, and oil; the teste-morte of one earth was said to taste like common salt.^[28]

Borelly promoted solvent analysis over distillation and objected to using the fixed salt of saltpeter in distilling earths.^[29] He and Dodart preferred lixiviating earths "in order to extract all the salt and all the various substances together in their chaos"; afterwards the earths could be rectified and purified so that their separate parts might be identified. Salts obtained thus could be used in numerous experiments.^[30] Any earth remaining after lixiviation could be tested further by solvents.^[31]

After Borelly criticized him, however, Bourdelin simply distilled fewer earths, while never adopting Borelly's method.^[32] Like the dispute over the relative merits of distillation and solvent analysis of plants, so the disagreement over the proper way of studying soils found Bourdelin and Borelly in opposition. Both disputes were resolved in Bourdelin's favor by his intransigence; Bourdelin would not abandon his preferred technique, despite the pressure exerted by his colleagues.