1914] BAILEY fir SINNOTT—PHYLOGENY OF ANGIOSPERMS 45 



resemble the normal stem of Fagus grandifolia 



numerous 



protoxylem subtend an equal number of multiseriate rays. There 

 is this difference, however, that in subsequent growth of the twigs 

 not all of these so-called primary rays increase in breadth as do those 

 of the vigorous seedling stem (fig. 3), peduncle (fig. 8), and beech 

 (fig. 1). The multiseriate rays which occur in the first annual ring 

 of the narrow depressed segments gradually decrease in width during 

 the next two years' growth and become uniseriate. 



The structure and development of rays in the first annual ring 

 of mature shoots are subject, as in the seedling stem, the root, and 

 the peduncle, to marked variations under different physiological 

 conditions. Thus wide rays show a strong tendency to become 

 more numerous and parenchymatous in vigorous, well nourished 

 shoots than in feeble, stunted, or suppressed twigs. 



TRAUMATIC REGIONS 



Jackson called attention to numerous cases of reversion to 

 supposedly ancestral types of structure under abnormal growth con- 

 ditions or as a result of traumatism. Jeffrey, working largely 

 with the interna] structure of the gymnosperms, has emphasized 

 the importance of traumatic reactions in the study of phylogeny. 

 His contribution upon recapitulations in those regions of the 

 plant which are assumed to be conservative, such as the root and 

 seedling, is particularly significant, since injuries in these regions 

 are said to recall ancestral characters when reversions cannot be 

 induced traumatically in the mature stem. 



The wound reactions of the Fagales are accordingly of interest 



aggregate 



been 



found by the writers that the stimulating and irritating effect 

 of certain types of injuries (whether mechanical or pathological) 

 often accelerates the development of wide rays. The results of 

 very severe injuries which have a marked distorting effect upon 

 the tissues subsequently formed by the cambium are in some cases 

 very different from these. Such injuries retard the development 

 of large rays, just as feeble or stunted growth has been shown to 

 retard the development of wide rays in seedlings and roots. 



