NO. I GROWTH LAYERS IN TREE BRANCHES — CLOCK ET AL. 



63 



A concurrent lens consists of a system of two or more lenses around 

 the circuit, not in contact radially (text figs, i, 5, 6, 7; pi. 36, fig. 2). 

 Commonly they lie between two complete, entire growth layers, and 

 represent localized cambial activity completely or partially simul- 



FiG. s. — TTC 33-6-a. Increments for 1942-1944. Variable number of gls on 

 different radii. 1942: see; 1943: msce; see; 1944: longs arc (probable varia- 

 tion in cambial activity producing no visible effect between points of arc) ; 

 msce; concurrent lenses. Sequence of sharp or diffuse contacts along numbered 

 radii : 



Other radii give different sequences. 



taneous but always occurring between the major episodes of cambial 

 activity. Although composed of two or more discrete lenses on a 

 particular cross section, the combination is considered a unit for pur- 

 poses of description in the chapter on multiplicity. 



