1889.] BOTANICAL GAZETTE. 5 



adds very considerably to the teaching resources of the insti- 

 tution. Steps are being taken for its immediate enlargement. 



The advances made in the recent past by the photographic 

 art suggested that the biological school should not only have 

 a place provided where it could take advantage of the help 

 there afforded in illustration, but where photography, as ap- 

 plied to scientific work, could be taught. 



During the past season the results in this direction have 

 amply confirmed the opinion as to the value of photography 

 in botany, both for reproducing microscopic appearances 

 and for the larger visions of field work. 



Development of cork-wings on certain trees. IV 



EMILY L. GREGORY. 



Physiology. 



The question of function can only be raised here, in case 

 this peculiarity of structure is sufficiently emphatic to render 

 it probable that some special object is to be gained from it. 

 Assuming this to be true, the difference in the morphology of 

 the three kinds described suggests a corresponding difference 

 in function. In connection with this, two important princi- 

 ples held by scientists of the present day are to be consid- 

 ered. First, that no peculiarity of structure in living organ- 

 isms is supposed to exist without adequate cause. For ex- 

 ample, the wings of Euonymus alatus, which appear to the 

 ordinary observer as useless if not cumbersome appendages, 

 may be accounted for as a result of an effort on the part of its 

 ancestors to accommodate themselves to their environment. 

 According to this, it is not necessary, however, to show that 

 an organ which proved advantageous to the ancestors of this 

 plant is of equal service now to the offspring, unless it can be 

 shown that the circumstances which called it into existence 

 are still unchanged. 



The second principle is that nature is extremely sparing 

 of material ; that of all the various means made use of to at- 

 tain an end, those requiring the least outlay of material are 

 the ones retained, and peculiarities of structure arising in 

 harmony with this principle are the ones transmitted by in- 

 heritance. 



Assuming the validity of these two principles, it would 

 seem a proper question to ask : Of what use to these plants 



