36 HISTORY OF BOTANY 



stand aU perpendicular, and so cross to the horizontal 

 fibres of all the said parenchymatous parts ; even as in a 

 piece of lace upon the cushion, the pins do to the threds. 

 The pins being also conceived to be tubular, and pro- 

 longed to any length ; and the same lace work to be 

 wrought many thousands of times over and over again, 

 to any thickness or hight, according to the hight of any 

 plant. And this is the true texture of a plant ; and the 

 general composure, not only of a branch, but of all other 

 parts from the seed to the seed." 



In view of the comparison of animal and plant skeletons 

 I have had occasion to make to you in connection with 

 the nature and distribution of mechanical tissues, it may 

 be of interest to quote Grew's ideas on the subject. In 

 his Cosmologia Sacra, published in 1701, he writes : — 

 "In the woody parts of plants, which are their bones, 

 the principles are so compounded, as to make them 

 flexible without joynts, and also elastick. That so their 

 roots may yield to stones, and their trunks to the wind, 

 or other force, with a power of restitution. Whereas the 

 bones of animals, being joynted, are made inflexible." 



The parenchyma Grew hkens to " froth of beer or eggs." 

 " The microscope more precisely shows," he says, " that 

 these pores are all, in a manner, spherical, in most plants ; 

 and this part, an infinite mass of Httle cells or bladders. 

 The sides of none of these, are visibly pervious from one 

 into another ; but each is bounded within itself." 



The structure of the vessels of the wood had a special 

 fascination for the early anatomists. Grew's conception 

 of a vessel was a ribbon wound spirally round a stick ; 

 the stick is then supposed to be withdrawn and the ribbon 

 left in the form of a tube. The young wood, he believed, 

 was formed from the inner layers of the rind, a view that 

 continued to be held for many a day. Grew was a remark- 

 ably acute observer, and as evidence of this I may refer to 

 his statement that in the spiral elements of the wood the 

 spiral thickenings in the root run " by south, from west 



