UNITED STATES DEPARTMENT OF AGRICULTURE 



DEPARTMENT BULLETIN No. 1131 



Washington, D. C. PROFESSIONAL PAPER February 13, 1923 



THE FORMATION AND PATHOLOGICAL ANATOMY OF FROST RINGS IN 

 CONIFERS INJURED BY LATE FROSTS. 



By Arthur S. Rhoads, formerly Assistant in Forest Pathology, Office of 

 Investigations in Forest Pathology, Bureau of Plant Industry. 



CONTENTS. 



Page. 



Introduction 1 



Review of the literature 2 



General symptoms and macroscopic 



appearance 5 



Page. 



Anatomical structure of the frost 



rings 8 



Summary 13 



Literature cited 15 



INTRODUCTION. 



Various writers have shown that an abnormal or pathologic 

 parenchyma tissue may occur as an interruption of the normal course 

 of the wood elements m the growth rings of coniferous trees, result- 

 ing from a variety of widely different causes, which may either 

 directly or indirectly influence the growth of the cambium. Among 

 these causes may be enumerated mechanical injuries of any kind; 

 attacks by various cryptogamic and phanerogamic parasites which 

 stimulate the woody tissue to an abnormal development; abnormal 

 physiological conditions of growth and nutrition which per se pro- 

 duce a like effect; premature defoliation; and injuries resulting from 

 such meteorological causes as lightning, frost, and drought. The 

 last-mentioned three forms of injury have rather distinctive anatomi- 

 cal characteristics which are scarcely recognized in this country 

 and additional knowledge of these is highly desirable. 



Owing to its close resemblance to the disturbances in the wood 

 caused by certain forms of lightning injury which he was studying, 

 the writer was impelled to investigate also the pathological anatomy 

 of late- frost injury. The present bulletin is therefore designed as 

 a contribution to our knowledge of the pathological anatomy of late- 

 frost injury in the conifers. 



The material used as a basis of this study was collected by the 

 writer in connection with his field work in various parts of northern 

 Idaho, northeastern Washington, and northwestern Montana and 

 was supplemented by material collected later in the District of 

 Columbia and in Missouri. The photomicrographs were made by 

 the writer from his own sectional preparations. 



18163—22 1 



