178 



PLANT PHYSIOLOGY 



These numbers, however, are much above the average, even 

 the Bamboo being a notoriously rapid grower. The extra- 

 ordinarily rapid growth of the stamens of wheat takes place 

 w r hen they are released from mechanical hindrance by the 

 spreading apart of the scales. 



Probably the average rate of growth for plants does not 

 exceed, if it equals, 0.005 mm. per minute. Certainly there 

 are many plants which grow so slowly that no one has had 

 the patience and skill to make accurate measurements. The 

 lichens are among such slow growers, though these must 



GO" 



30,u 



20/i 



70.03 



g o 



Figure 12. Curve of growth in part of a filament of Bacillus ramosus. 

 (From Ward.) 



grow at different rates as is evident in the parts of California 

 where the very large " lace-lichen" (Rainalinti reticuhita) 

 and crustaceous and small foliose lichens live side by side. * 

 In connection with these figures as to the rate and the 

 percentage of growth of larger and in some cases "higher" 

 plants, it may be of some interest to compare the curve of 

 growth obtained by Marshall Wardf while studying bacte- 

 ria. The accompanying diagram gives the curve of growth 



* See Peirce. G. J. On the mode of dissemination and on the reticu- 

 lations of Itamalma reticulata. Bot. Gazette, vol. XXV., 1898. Ditto. 

 The nature of the association of alga and fungus in lichens. Proc. -Cal. 

 Acad. Sci.. Series III., Botany, vol. I., 1899. Ditto. The relation of fungus 

 and alga in lichens. American Naturalist, vol. XXXIV., 1900. 



tWard. H. M. On the biology of Bacillus ramosus. Proc. Roy. So- 

 ciety vol. LVin.. 1895. 



