(38) 



Floor-cases Nos. 10 to 12 and wall-case No. 5 contain 

 plant remains of Neozoic time. Those of the early Ter- 

 tiary Period (Eocene) are displayed in floor-case No. 10. 

 Those of the later Tertiary (Miocene) and Quaternary 

 Periods in floor-cases Nos. 11 and 12. The specimens in the 

 latter case complete the sequence of plant life on the earth 

 and bring it up to modern times. A number of specimens at 

 one end of the case show the methods of preservation by 

 petrification, incrustation and carbonization, and on the upper 

 shelf is a series of specimens from Quaternary and more 

 recent swamp deposits which show how the conversion of 

 living plants into fossils, a process now going on, has its 

 beginning. 



The specimens in wall-case No. 5 further illustrate the 

 characteristics of the plants of the late geological periods and 

 the methods by which the various plant structures have been 

 preserved. A number of specimens of silicified woods show 

 the method of preservation by what is known as petrifaction, 

 or conversion into stone, in which the woody structure is 

 replaced by mineral matter. Other specimens show preser- 

 vation by incrustation, in which mosses and the stems of reeds 

 are coated or incrusted by mineral matter deposited from 

 springs; while on the upper shelf and on the top of the case 

 are logs and stumps from old swamps and interglacial depos- 

 its, in which the wood has been partially carbonized, or con- 

 verted into lignite, by the slow process of natural distillation. 

 This process represents the beginning of the conversion of 

 vegetable tissue into coal. 



LECTURES 



Other features of the museum building include the large 

 public lecture hall, with a seating capacity of over seven 

 hundred, which occupies the western end of the basement. It 

 is equipped with an electric projection-lantern, and public 

 popular lectures covering a wide field of botanical and horti- 

 cultural subjects are delivered here on Saturady afternoons 

 in autumn and spring; these are fully illustrated by means 



