l88 9-J BOTANICAL GAZETTE. ^ 



Wfi aCh °i ^ Ia , WS ° fevolution ' Pays one of Nature's heav 

 S? eS /Tl° S ? S the ° r ^ ans h once had. 



i«//. //o/j^ .w ^ ^/^^ ^ ^^ Mass 



Explanation of Platf vrrr i?;^ i *^ * i 



from seed. Fis 2 tin of root ,if \, 7 * g ' I* m 2 tur ? embl TO, dissected 



Development of cork-wings on certain trees. V. 



EMILY L. GREGORY. 



* 



damhnr l g n ° W 1- ? m StemS > ° f this f 3'P e t0 th °se of Liqui- 



suTs H' 1S re ! d,ly S6en that whate ver may be the end re- 

 sume «« inT C r atC CaUSGS P T roducin S th e wing are not the 



m£Lrf r f ° rmei " 1 - 3pe ' ItS ecceQ t™ development is a 



marked peculiarity, which, so far as I have been able to dis- 



ar7ses' 2l m u° ° ther instance - The question at* once 



Growth- *i * the 1 causes which Produce^ eccentricity 01 



growth in the annual rings of wood are likely to extend to 

 the tissues arising from the cork cambium. If this were 

 nrnlT t0 , b « the case h . m] S ht help but little in solving the 



p oblem before us, as it is a well known fact that the best 

 authorities do not agree as to the causes of eccentric growth 

 in woody tissues. to 



f« ,i The function of protection which is universally assigned 



to the periderm naturally requires greater flexibility of struc- 

 ture, varying degrees of thickness, greater or less permea- 

 bility for water and gases according to varying outward 

 ^ndmons, and, finally, greater or less outlay of material, 

 which in some cases, is retained, in others, discarded bv the 

 Plant atter it has performed its function. In this way it is 

 easy to account for the variableness in periderm forma- 



22L- M lll , llstrated in the genus Euonvmus. This is more 

 striking when contrasted with the uniformity prevailing j„ 

 the structure of woody tissue. For example, when examin- 

 ing a large number of woods in regard to the presence or 

 absence of bordered pores in the libriform, it was found 

 quite unnecessary to carry the study farther than the genus. 

 ' a Sln g ,e species contained libriform with bordered pores 

 this, was sufficient for the genus. 



