258 Mr John Eattray on Evolution of Oxygen hy Sea- Weeds. 



from the above, is not unlikely; but since all the experi- 

 ments have, so far as practicable, been carried out in the 

 same manner, a comparison of the figures may prove of 

 some interest. Thus by combining the averages in the case 

 of B7iteromorpha, Viva, Porphyra, and Conferva, obtained 

 above, a general average of 56"5 per cent, of oxygen is 

 found — a figure which may accordingly be taken as fairly 

 representing the summer and early autumn evolutions of 

 these plants. By similarly combining the averages got for 

 the second series of experiments with Ulva, and those with 

 Fucus and Chondrus, a general average of 37"3 per cent, is 

 obtained, which, as in the previous cases, may be taken as 

 representative of the evolutions at the more inert stages of 

 growth during the colder seasons of the year. A much more 

 extensive series of observations must be made before an 

 adequate conception of the oxygenating power of these com- 

 paratively lowly organised forms of life can be obtained, but 

 that their capacities in this respect merit careful study is 

 at once apparent from the foregoing tables. In the calcu- 

 lations no account lias been taken of the volume of the sea- 

 weeds experimented with, the only problem being the 

 determination of the amount of oxygen present in the 

 entire volume of gases collected, it being clear that that 

 this proportion will remain the same for the same species 

 under the same circumstances, whether the volume of the 

 algae be large or small. 



On the Development of BifoUar Spurs into ordinary Buds 

 in Pinus sylvestris. By Professor Alexandre Dickson, 

 M.D., LL.i). 



(Read February 12, 1885.) 



Many Coniferse exhibit remarkable specialisation as 

 regards branch development. In some, such as Larix and 

 Cedrus, there is a marked tendency to a contracted develop- 

 ment, or shortening of many of the shoots which appear as 

 " spurs," with numerous leaves crowded together to form a 

 fascicle. Here it is only certain of the shoots which are 

 developed in this way, and of these it may happen that a 

 spur of one season may next season become produced at its 

 extremity in the ordinary elongated form with scattered 



