A Comparative Study of the Wood Structure of Several South American Species of Strychnos

Cockrell, Robert A.

doi:10.2307/2437058

Cited by 5 publications

(1 citation statement)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A similar origin is well described by Balwant Singh (1943) for Leptudenia, who emphasizes the continuity of the radial rows derived from the cambium both towards the centre of the stem and towards the outside. This is in contrast to the condition found in phloem islands produced by the second method, which has been described for Strychnos (Scott & Brebner, 1889; Cockrell, 1941). (Fig.…”

Section: (B) Anomalous Typescontrasting

confidence: 75%

The Ontogeny of the Vascular Cambium in the Stem of Seed Plants

Philipson

Ward

1965

Biological Reviews

View full text Add to dashboard Cite

Summary 1. A striking characteristic of the vascular cambium is its plasticity. It may arise in any position in any tissue except the epidermis. It may function in a variety of ways, giving rise to xylem or phloem alone, or to both tissues. If both xylem and phloem are formed from the same cambium, they may be derived from opposite faces of the meristem or be combined as bundles or be mixed less regularly. One cambium may be succeeded by another and the method of functioning of successive cambia may vary. A number of these possibilities may be combined in one plant either simultaneously or at different stages of growth. 2. The mode of operation of the cambium in monocotyledons is so different from that of most dicotyledons, that it is unlikely that they can be homologous. It is probable that a cambium has been acquired independently in several lines of mono‐cotyledonous evolution, although the virtual identity of the cambium wherever it occurs in monocotyledons is remarkable. Some dicotyledonous cambia are almost equally distinctive. To distinguish these from the usual bi‐directional cambium, the term uni‐directional cambium is applied to them in this account. A uni‐directional cambium may be a primitive feature of the families Chenopodiaceae, Amarantaceae, and Nyctaginaceae, but essentially identical cambia have been acquired in the Styli‐diaceae, the Phytolaccaceae and in several independent lines within the Compositae. 3. Another feature of the cambium is the pressure of competition between its cells. This is especially evident during the early growth of a stem, when increase of circumference is relatively great. Many cells are produced by pseudo‐transverse divisions within the initial layer. These cells increase in size by intrusive growth, and many are lost. Survival has been shown to be influenced by a wide variety of factors. 4. A large number of investigations has established a pattern of variation in size of xylem elements within the tree. This reflects a similar pattern of size variation in the cambium. In broad outline this pattern is found in most trees which have been investigated, although considerably modified in timbers derived from storeyed cambia. Groups of woody plants showing other modifications of the pattern have been described. 5. The transformation of fusiform initials into ray initials and vice versa is another example of the plasticity of the cambium. The maintenance of the proportion of ray to fusiform initials characteristic of a species indicates that cambial activity is a well‐co‐ordinated and orderly process. The importance of a correct proportion of ray tissue among the longitudinal elements of the xylem is evident.

show abstract

Section: (B) Anomalous Typescontrasting

confidence: 75%