Mariotte concluded that the primary sap finds its way into
the plant through the leaves as well as through the roots from
the fact, that if a branch is taken from a tree, and one of its
smaller branches kept in water, another will remain fresh for
some days; the conclusion was not quite justified, as the
future showed. His remarks on the necessity of sunlight
to nutrition, on the ripening of fruit, and other matters, rests
on very imperfect experience and need not be noticed.
The characteristic and the important point in Mariotte's theory of nutrition is the marked contrast between his point of view in natural science and the Aristotelian and scholastic doctrines still widely diffused, and thus he is led to declare war also against Aristotle's vegetable soul. He connects his remarks on this point with a fact which excites his astonishment, namely that every species of plant reproduces its properties so exactly; no explanation of this fact, he says, is gained by the assumption of a vegetable soul, of which no one knows what it is. He declares as decidedly against the theory of evolution, also much in vogue in his day. In opposition to the notion that all future generations are shut up one inside another in the seeds of a plant, he thinks it much more probable that the seeds only contain the essential substances, and that their influence on the crude sap brings about the successive formation of the rest of the constituents of the plant, a view which we may still allow to be correct. He regards the whole process of nutrition and life in plants as a play of physical forces, as the combination and separation of simple substances, but he believes at the same time that he can prove the commonly received doctrine of spontaneous generation to be a necessary conclusion from this view. On this point he went wrong from want of sufficient and well-sifted experience, for he regarded it as a proof of generatio spontanea that numerous plants spring up from the soil thrown out from ditches and swamps that have been laid dry. 'We may therefore suppose,' he says, ' that there are in the air, in the water,
