DEVELOPMENT OF VEGETATIVE AND FLORAL BUDS 259 



tion are those of Robert Brown and his co-workers. In the past two 

 years, they have made comparative growth studies on the apex of 

 Lupinus albus (Sunderland and Brown. 1956). As defined for their 

 studies, the apex included the apical meristem or dome and the first 

 seven nodes and internodes below. Determination of cell numbers, 

 average cell volumes and total volume in the apical dome, the suc- 

 cessive leaf primordia and the apical units (e.g.. the first apical unit 

 would include the apical meristem or dome and the axis with the 

 first leaf primordium; the second apical unit, the apical dome with 

 that part of the stem bearing the first two leaves; and so on) has 

 enabled them to compare on a cellular level, or at least approach a 

 comparison of, the growth of individual successive primordia with 

 their respective subjacent internodes, that is, growth units. A second 

 study (Sunderland et al., 1956, 1957) has enabled these investigators 

 to get a picture of the concentration of protein and of the related 

 respiration rates in the apical dome, in apical units, in growth units, 

 and in their component parts, the leaf primordia and internodes, the 

 oxygen uptake being determined through the use of minute Cartesian 

 divers. The importance that they attach to their findings can be 

 indicated in their statement (1957, p. 69), "Clearly many of the 

 properties of the system are a consequence of the state established in 

 the first growth unit, and the origin of the differentiation in this unit is 

 a matter of critical importance." The first growth unit consists of the 

 small-celled first leaf primordium and a central portion, which is the 

 initiating stage of the first internode. As the authors indicate (1957, 

 p. 69), "Thus the position in the first primordium is Hkely to repre- 

 sent the situation in the surface of the system, and the position in the 

 internode is likely to be determined by the cells of the central core." 

 While it is true that the authors take no note of the central zone of 

 the apex as different and distinct from the pith of the first four 

 internodes and of the small-celled pith rib meristem that separates the 

 central zone from the internodal pith below, yet one cannot but be 

 arrested by the findings of the high oxygen uptake reported for the 

 predominantly large-celled region in the first four internodes. In fact, 

 a recent personal communication from Dr. Brown indicates that in 

 Lupinus the oxygen uptake in this large-celled middle region is some 

 20 times as great as that in the small-celled peripheral leaf primordia. 



