19 1 2] JONES—DIANTHERA 15 



them. The leaves of the seedlings correspond very closely to those 

 of the mature plant. The latter have been fully described by 

 Holm. One correction must be made, however. Holm says 

 (5, p. 326) "collenchyma and stereome seem to be entirely absent 

 from the lateral portion of the blade/' apparently overlooking the 

 marginal strand of collenchyma occuring in both seedling and adult 

 leaves (fig. 32). 



The axillary buds 



It has already been mentioned that buds are usually formed in 

 the axils of the leaves. In most cases, except at the base of the 

 plant, these buds, after having developed one or two pairs of very 

 small leaves, remain dormant. Several of the basal buds may 

 develop, giving rise to the horizontal rhizomes, by means of which 

 the plant perennates. The bud arises as a small mound of tissue 

 in the axil of the leaf. On this mound there soon appear the prim- 

 ordia of a pair of opposite leaves, whose plane of symmetry is at 

 right angles to that of the subtending leaf. A single leaf trace from 

 each leaf is differentiated, and passing downward becomes inserted 

 between the trace of the subtending leaf and an arm of the forked 

 bundle of the stem. 



As in the main stem, the next step in development is the differ- 

 entiation of a pair of forked bundles, the forks of the outer bundle 

 being inserted between the first pair of leaf traces and the trace of 

 the subtending leaf. The arms of the other forked bundle become 

 inserted behind the first pair of leaf traces, between them and the 

 forks of the stem bundle. As in the stem, a pair of traces from 

 the second pair of leaves now differentiate, and become inserted in 

 the crotch at the top of the forked bundles. By this time it is seen 

 that a very irregular sheath is forming around each of the bundles 

 of the lower part of the bud (fig. S3)- On entering the node below, 

 these sheaths open on the inside, the ends connecting so as to form 

 a complete sheath surrounding the bundles of the bud and the trace 

 of the subtending leaf (fig. 34). Lower down, this sheath opens 

 on the inside, the ends connecting with those of the opening sheaths 

 of the "forks" of the stem. This forms a complete sheath around 

 all of the bundles, as is shown in fig. 35. The endodermis now 

 behaves in the way already described in a node which had no bud. 



