MALPIGHI 149 



that they consisted of spiral vessels filled with air. This 

 incident is supposed to have led him on to study the 

 structure of wood, and the general anatomy of plants. 

 It has no more claim to belief than the famous legend of 

 Newton and the apple. In his own narrative Malpighi 

 drops all the picturesque circumstances, merely saying 

 that while lodging in the villa of the viscount he 

 examined the structure of plants, and in a bit of 

 chestnut wood met with wide air-ducts or tracheae, 

 which he also found in other vegetables. It is probable 

 that what Malpighi had seen (perhaps in a shaving of 

 chestnut wood) were not true spiral vessels, which are 

 found only in the primary wedges, but pitted ducts. 

 Finding that these ducts were often full of air, which 

 escaped when the parts were cut under water, and that 

 in some cases they were packed with cells (the ttillen or 

 tyloses of modern botanists), he was struck with the 

 resemblance to the wind-pipe of an air-breathing verte- 

 brate, the air-tubes of an insect and the air-cells of a 

 vertebrate lung, and wrote to his friend Borelli that he 

 had discovered the respiratory organs, which served also 

 to carry the sap. He further remarked that by snap- 

 ping a green stem across and drawing the cut ends 

 gently apart, the spiral thread of the vessels is easily 

 demonstrated. ^ Many generations of succeeding botanists 

 have been accustomed to verify this fact upon the young 

 shoot of the elder.^ In 1671 he sent to the Eoyal Society 

 what he called the Idea or preliminary sketch of an 



'^ Anat. Plant. Idea, p. 3. 



^Sprengel, Cuvier, Sachs, and perhaps other historians of Botany mention 

 Henshaw as the discoverer of spiral vessels in walnut-wood (1661). The only- 

 ground for this statement, and so far as I can find out, the only record of 

 Henshavr's work in botany, is this minute of a meeting of the Royal Society 

 (July .31, 1661) : — "Mr. Henshaw exhibited the spirals of nut-trees, showing 

 that they grow snail-wise" (Birch, ^isi. o/i?oy. Soe. Vol. I, p. ,37). These 

 spirals must surely have been hazel-stems strangled by honeysuckle. 



