Structure and Growth of the Vegetative Shoot Apex of Garrya Elliptica Dougl

A Comparative Study of Vegetative Shoot Apices in the Rosaceae

“…Philipson (1946) suggested for Bellis and again in a review paper (1947) that the corpus of angiosperms has a central initiation zone of large, lightly staining cells, above a pith rib meristem, surrounded on the periphery by a zone of cells (flanking rib meristem) with very dense contents. Boke (1941) , Ball (1941) , Reeve (1942) and Hsii (1944) described a similar situation in the plants which they studied. Also, Majumdar (1942), Reeve (1948) and Millington and Gunckel (1950) found that the central initial cells included both the tunica and the corpus in their investigations.…”

“…For example, as mentioned before, flowers (terminal) are not formed in Rosa until after the buds open in the spring, but the terminal shows tunica variation between the active and the perennating condition. Variation in tunica stratification has been commonly reported, as reviewed by Reeve (1942Reeve ( , 1948 and Philipson (1949). The present study shows a general variation in the number of tunica layers throughout the family or even within one species, ranging from the one tunica layer of Prinsepia uniflora to the occasional six layers of Crataegus crus-galli.…”

Leaf Initiation, Origin, and Pattern of Pith Development in the Rosaceae

“…Also, there was no correlation between the height of the apex and the number of tunica layers. Variation in tunica layering during one plastochron, as reported by Reeve (1942Reeve ( ,1948, remains to be discussed in the Rosaceae. Seasonal changes, other than in tunica layers, were noted in the configuration of the pith rib meristem.…”

“…DISCUSSION.-Tunica layering during one plastochron was investigated in the Rosaceae on plants having alternate and opposite leaves and varying numbers of tunica layers. Reeve (1942Reeve ( , 1948 was able to demonstrate for Garrya ellipticaand Salix laevigata that the number of tunica layers fluctuates in conjunction with leaf initiation and development.…”

“…and in close proximity to each other thereby imparts a flattened aspect to the apex. Reeve (1942Reeve ( , 1948 was able to show that the number of tunica layers in an apex may fluctuate during initiation and development. The term plastochron as reported by Schiiepp (1916) designated the time interval between the formation of successive leaf primordia.…”