The anatomical structure of the common fir (Abies alba Mili.) bark. I. Development of bark tissues

Qualitative and quantitative changes in bark tissues of the fir (Abies alba) connected with the long-term cambium activity were investigated: 1) the development of secondary phloem elements forming the annual ring in different-aged parts of the stem was studied in detail; 2) the terms of formation of the phloem elements were established as well as the duration of the periods of their differentiation and functioning; 3) observations were made of the changes occurring in nonconducting phloem and primary cortex tissues; 4) the course of development of the periderm was studied