REVIEWS 19 



"its availability, may at times be limiting to the successful functioning of the 

 plant. 



' Carrying the idea of holocoenotic environments further, the author brings 

 in the concept of "compensation" of factors. Here it is presumed that through 

 the interaction of factors an adverse condition of one factor is compensated for 

 by readjustments in the responses to other factors to meet the deficit. One 

 naturally is curious as to how the factor can make its deficit felt to the extent 

 of initiating compensation if a single factor cannot be limiting. In view of the 

 genetic problems so ably discussed by the author, it would seem that the ex- 

 amples- of extra-limital distribution used to illustrate compensation cannot be 

 explained on the basis of compensation of factors. It would be necessary to es- 

 tablish beyond a reasonable doubt that the persistence through reproductive 

 activity of any species or group of species in any given habitat is ever extra- 

 limital. It would be more logical to seek an explanation in terms of ecotypes 

 of one sort or another. 



Considerable space is devoted to the discussion of recent work in the field 

 of paleobotany and various methods of research are presented. Much of this 

 paleobotanical work has not as yet been sufficiently subjected to scientific scru- 

 tiny to be properly evaluated. The author, however, does an excellent job of 

 presenting the material. The chief difficulty is that too few minds have met 

 over the problems involved so that in many cases the ideas expressed in the 

 papers reviewed can scarcely be regarded as mature. In a sense the methods 

 of the paleobotanist tend to make this difficult because the field worker, in col- 

 lecting a flora, is the only one who sees the record unfold. He alone is present 

 to evaluate' the significance of the position of the material in the record. 

 Too often he alone decides what to keep and what to discard. What he keeps 

 often depends upon such factors as transportation and storage facilities. Any 

 further discussion or elaboration of this flora by later workers has imposed 

 upon it the limitations in judgment of the field collector. The preoccupation of 

 many paleontologists with key fossils also has imposed a disastrous handicap 

 on the values of these floras and faunas for geographic and ecologic interpreta- 

 tion. 



In the discussion of endemism, it seems to your reviewer that the author 

 begins with a false assumption, namely, that endemics are either youthful spe- 

 cies or relics. What about all of those endemics in the prime of their species 

 life that may occupy completely, all of their very specialized potential area? 

 What about this vast array of edaphic species, — an aspect of the problem that 

 to your reviewer seems to be of far greater significance to the general subject 

 of endemism than is the problem of youth and old age? Is it a result of youth 

 or old age that so many Eastern United States endemics are associated with 

 the same ecological factors that cause pine barrens? Is it a consequence of 

 species age that so many Californian endemics are associated with ferro-mag- 



