and ConclusionsI have no information regarding the gametophyte, nor have I examined the structure of axis and leaf in young plants. It must therefore remain to be seen what light such data may throw upon the problem of the phyletic place ofDeparia Moorei. The nature of the stele, the leaf-trace, and the venation, in very young plants, would also present points of value. But it will be at least evident that the vascular system of the axis is, in mature plants, of an advanced type, and it may

more »

... onably be affirmed that the marked variability in the degree of dictyostely is an index of an inherent plasticity. It seems reasonable to suggest that the reductions in size, and simplification of structure in the direction of solenostely shown in fig. 40, is related to the cultural conditions. The plant from which the material was derived had lost ground both in size and healthiness of its leaves.