192 STRUCTURE AND LIFE HISTORIES 



which arise from the study of so lowly an organism as a 

 fern. Some of these have been partially solved — prob- 

 ably none of them has been completely solved. In fact, 

 we may say that our ignorance of life-processes greatly ex- 

 ceeds our knowledge. Very much more remains to be 

 ascertained than has already been found out; for example, 

 what is protoplasm? Nobody really knows. We have 

 analyzed the substance chemically, we have carefully 

 examined and tried (but without complete success) to 

 describe its structure. We know it is more than merely 

 a chemical compound. It is a historical substance. A 

 watch, as such, is not. The metal and parts of which a 

 watch is made, have, it is true, a past history; but the 

 watch comes from the hands of its maker de novo, without 

 any past history as a watch. But not so the plant cell. 

 It has an ancestry as a cell; its protoplasm has what we 

 may call a physiological memory of the past. It is what 

 it is, not merely because of its present condition, but 

 because its ancestral cells have had certain experiences. 

 We can never understand a plant protoplast merely by 

 studying it; we must know something of its genealogy and 

 its past history. 



What is the origin of the sporophyte, and how did 

 there come to be two alternating generations? What is 

 the meaning of fertilization; what the mechanism and 

 laws of inheritance? How did there come to be on the 

 earth such plants as ferns? What was the origin of Hfe? 

 What is Hfe? No one can give complete answers to these 

 questions; but the purpose of the study of botany is to 

 help fit us to seek the answers intelHgently. To those 

 who are interested in problems of this sort, nothing can 

 be more fascinating, nor more profitable. 



