Mason — Ligneous Zonation mid Die-Back in the Lime, West Indies. 259 



marked in the right-liand side of the section. These bands are again grouped, 

 and are not especially marked. It would seem that they originate as a result of 

 regularly recurring periods of desiccation. A certain similarity between this 

 section and that from the Lime Experiment Station at Koseau, Dominica, can 

 be traced in the radial distribution of the vessels; the vessels are, however, 

 distinctly smaller in diameter, and, moreover, the parenchyma bands better 

 defined. Both characters may be due to a more pronounced aridity in the 

 environment (cf. 6). 



Belle Field, Gkove Estate, Montsekrat (fig. 6, Plate XV). 



Lime trees exhibiting die-hack. 



The soil is of the talus slope type, free from large stones, and in good tilth. 

 The sit^iation is exposed to ivinds, and the existing artificial wi^id-helts appear 

 to he inadequate. It was here that certain cultural and spraying experiments, 

 designed with a view to suppressing attacks of scale insects, were inaugurated 

 in 1915. 



Mean Annual Rainfall — 58 inches. 



Xylem Cylinder. 



This section resembles that just described from the Grove Botanic Station, 

 Montserrat, in the diameter and radial distribution of the vessels. It differs, 

 however, in one respect. The parenchyma bands are more sharply delimited, 

 and do not occur in groups along the radii. If it be again assumed that these 

 bands of tangential parenchyma originate during periods of pronounced desic- 

 cation, it may possibly be inferred from their more irregular distribution that 

 the activity of the cambium was checked at irregular intervals in the course of 

 the year, and not alone for a short period during the dry season. It is also 

 necessary to assume that these checks in growth wex'e of greater duration than 

 in the case of the Grove Botanic Station. 



It will be observed that Hardy states that the situation is exposed to winds. 

 It is quite conceivable, therefore — for the conductivity of the wood is evidently 

 small — that growth may have been checked at any period in the course of the 

 year, even though the water-supplying power (5) (7) of the soil was adequate. 



Olveston, Montserrat (fig. 7, Plate XV). 



Lime trees exhihiting die-hack. 



This locality is situated on the gently sloping side of an exposed low hill 

 near the sea-coast. The soil is very shallow and rocky. The lime trees have 

 heen planted chiefty in pockets of soil. At the time of sampling (AjDril, 1921) 

 the soil was very dry and compact. 



Mean Annual Rainfall — 60 inches. 



Xylem Cylinder. 

 In this section there is little or no regularity exhibited in the zonation. It is 

 possible to infer only one thing, namely^ that the activity of the cambium was 

 repeatedly interrupted, presumably &s a result of irregularly recurring periods 

 of desiccation, due, no doubt, to the exposed position of the field. 



Saltoun, 9-acre plot, Dominica (fig. 8, Plate XVI). 



Lime trees exhihiting die-back. 



The soil at Saltoun is shallow, and overlies sheet rock. The subsoil is a 



