358 Mr. Ruskin [April 19, 



WEEKLY EVENING MEETING, 

 Friday, April 19, 1861. 



Sir Roderick I. Murchison, D.C.L. F.E.S. Vice-President, 

 in the Chair. 



John Ruskin, Esq. 

 On Tree Twigs. 



The speaker's purpose was to exhibit the development of the common 

 forms of branch, in dicotyledonous trees, from the fixed tyi^e of the 

 annual shoot. Three principal modes of increase and growth might be 

 distinguished in all accumulative change ; namely : — 



1st. Simple aggregation, having no periodical or otherwise defined 

 limit ; and subject only to laws of cohesion and crystallization, as in 

 inorganic matter. 



2nd. Addition of similar parts to each other, under some law fixing 

 their limits and securing their unity. 



3rd. Enlargement, or systematic change in arrangement, of a typical 

 form, as in the growth of the members of an animal. 



The growth of trees came under the second of these heads. A 

 tree did not increase in stem and bough as the wrist and hand of a 

 child increased to the wrist and hand of a man ; but it was built up by 

 additions of similar parts, as a city is increased by the building of new 

 rows of houses. 



Any annual shoot was most conveniently to be considered as a 

 single rod, which would always grow vertically if possible. 



Every such rod or pillar was, in common timber trees, typically 

 either polygonal in section, or rectangular. 



If polygonal, the leaves were arranged on it in a spiral order, as in 

 the elm or oak. 



If rectangular, the leaves were arranged on it in pairs, set alter- 

 nately at right angles to each other. 



Intermediate forms connected each of these types with those of 

 monocotyledonous trees. The structure of the arbor vitce might be 

 considered as typically representing the link between the rectangular 

 structure and that of monocotyledons ; and that of the pine, between 

 the polygonal structure and that of monocotyledons. 



Every leaf during its vitality secreting carbon from the atmosphere, 

 with the elements of water, formed a certain quantity of woody tissue. 



