851- aEPOKT — 189-j. 



division of the nucleus in the spore-mother cells of plants. The wax employed is 

 made of a mixture of one part of white wax, with five parts of paratiin, the melt- 

 ing point of which is about 60° C. 



SATURDAY, SEPTEMBER, 14. 



The Section did not meet. 



MONDAY, SEPTEMBER 16. 



A joint discussion with Section B was held on the Relation of Agriculture to 

 Science. See p. 660. 



The following Papers were read : — 



1. Oil the Destruction of a Cedar Tree at Kew by Lightning. 

 By W. T. "Thiselton-Dyer, F.R.S. 



The President of the Section exhibited photographs and specimens of a large 

 cedar ( Cedrus Deodara, Loud.) from Kew, which had been struck and completely 

 shattered by lightning on August 10. It was pointed out that the main stem had 

 been in part blown into matchwood by the violence of the shock, and branches 

 were torn off with large portions of the trunk adhering to their base. The explo- 

 sion seemed to have been centrifugal, the stem having been disrupted from the 

 centre, and not merely stripped superficially. . 



2. On the Formation of Bacterial Colonies. 

 By Professor Marshall Ward, F.R.S. 



The author has examined the details of development of the colony in numerous 

 species from a single spore by employing microscopic plate-cultures, which can be 

 kept under observation with a one-twelfth and even a one-twentieth oil-immer- 

 sion lens, or by making pure Klatschpraparate on cover-slips covered with a thin 

 film of gelatine. 



He finds many factors of importance affecting the form, extent, rapidity of 

 growth, and other characters of colonies ; the elasticity of the gelatine, the presence 

 of moist films on the surface of the gelatine, the rate of (slight) liquefaction, &c., 

 all being of importance in explaining the shapes, &c., of submerged colonies — ' whet- 

 stone shaped,' moruloid, spherical, or lobed colonies — the mode of emergence and 

 spreading over the surface of the gelatine, the formation of radiating fringes, irides- 

 cent plates, &c. 



Exposure to light during the development of liquefying colonies may pro- 

 foundly affect their shape and other properties, a phenomenon closely connected 

 with the retardation of liquefaction and growth. Pigment bacteria may give rise 

 to perfectly colourless races when cidtivated under certain conditions, and the colour 

 restored by again changing the conditions ; a fact which the author has not only 

 confirmed with red forms, but which he shows to be true of a violet bacillus. 

 Species commonly described as non-motile show active movements under certain 

 conditions, and the sizes of bacteria are not constant in different regions of one 

 and the same colony. Details have been worked out for series of types the ex- 

 tremes of which differ considerably in liquefying power, and essential difference 

 in the appearance of a colony may depend on the amount of liquefying power 

 e\inced. 



