USE OF THE MICROSCOPE IN BOTANY. 19 



globe, and like most vegetable cells consists of a 

 membranous bag with some fluid contents. The 

 vegetable cell-wall is generally composed of two layers 

 having different properties and composition. They 

 are excessively thin, and difficult of detection, unless 

 you add iodine or other colouring matter. The inner 

 layer, which can only be separated from the outer one 

 "by developmental changes, or by the influence of 

 re-agents which cause it to contract by drawing forth 

 part of its contents," is called the primordial utricle, 

 as " being first formed and most essential to the 

 existence of the cell." The outer cell is supposed to 

 be merely a protective covering ; the contents of the 

 cell consist of colourless protoplasm (organisable 

 fluid), containing albuminous matter in combination 

 with starch, gum, sap, and a green, oily substance 

 called chlorophyl. But let us return to the yeast cells. 

 They are still of the same form as when we looked at 

 them before, and independent of each other. I will 

 add a little newly-made beer, or some albuminous 

 matter mixed with sugar, and what do we see after the 

 interval of a few hours ? No longer single uncon- 

 nected globules, but a number together forming 

 chains. Each cell has budded out one or two little 

 projections, which have developed themselves into 

 complete cells, in their turn giving origin to fresh ones, 

 and so on continuously as long as the fermenting pro- 

 cess continues. When this is stopped, the yeast-plant 

 it is a fungus called Torula cerevisicz returns to its 

 isolated condition once more. In quoting an extract 

 from Dr. Carpenter, I mentioned the term protophyte* 

 The yeast fungus is a good example of organisms 

 designated by this word, which, as its derivation 

 shows, is intended to define the most simple, primi- 



* From TrpoiTor, " first," and <J>VTOV, "a plant." 



B 2 



