38 HISTORY OF BOTANY 



benefit to the insect of these visits he missed entirely the 

 advantages that accrue to the plant. The inward meaning 

 of the give and take was not appreciated until the days of 

 Conrad Sprengel, more than a century after Grew's time. 



Having discussed Grew's work so fully it will not be 

 necessary for me to spend much time over that of Malpighi. 

 His conception of the anatomical structure of the stem 

 resembles very closely that put forward by Grew. The 

 outer part of the rind or cuticle, he thinks, consists of 

 " utricles " laid down in horizontal rows, followed by 

 layer after layer of " fibres," each fibre composed of 

 tubes which open into each other. These layers form a 

 network, the meshes being filled with roundish tubes. 

 The wood which, like Grew, he thinks is formed by 

 transformation of the inner rind, consists of fibres and 

 tubes in longitudinal rows. Anastomosing spaces are left 

 between the fibres and these are filled with bundles of tubes 

 which run from the rind to the pith. These are obviously 

 Grew's " inserted pieces " and our medullary rays. Among 

 the bundles are " spiral tubes " in various situations but 

 mostly in concentric circles ; these are apparently the 

 large tracheae of the spring wood, in which, strangely 

 enough, he also managed to persuade himself that he had 

 seen a kind of peristalsis taking place. In some parts 

 Malpighi found other tubes containing milk, gum, turpen- 

 tine, etc., and in others still he recognised minute utricles or 

 bladders, which you are familiar with under the name of 

 tyloses, but which he compared with the alveoli of the lung. 



Malpighi gives the first published account of stomata, 

 so far as I can find, for Grew merely refers to these organs 

 as " orifices or passports." Malpighi says, " Among the 

 vessels and network of fibres in most leaves are distributed 

 special little air follicles or gaps which pour out either 

 air or moisture. These gaps are especially evident in the 

 leaves of the Oleander, where each area has four to many 

 pores or mouths, the whole surrounded by a margin bear- 

 ing numerous hairs," and on one of his plates the crypts 



