Leonakd — Genus Taenitis, ivith Notes on remaining Taenitidinae 257 



those towards the distal end, and they are crowded together in such a way 

 as to suggest intercalary growth. On the older part of the stem are found 

 simple scales. The distal portion of these is similar to that of the hairs, and, 

 like them, it terminates in a glandular cell. The hasal portion consists of a 

 number of cells adjoining one another to form a simple plate (Plate XV, B, 

 2 & 3). Intermediate forms between the hair and the scale are also found ; 

 some in which there is a doubling of the basal cell and others in which there 

 may be three or more cells at the base (Plate XV. B, 4 & 5). It is thus 

 necessary to correct previous statements on this point, such as those of Christ 

 ((2), p. 130), and of Diels ((5), p. 304), both of whom describe the rhizome 

 as bearing hairs only. 



Anatomy. 



The Stem. — In young steins a solenostele is found (Fig 1, i, & Plate XV, 

 Fig A). The ground tissue, both of the cortex and within the vascular 

 ring, is solerotic, with the exception of two or three rows of cells adjoining 

 the endodermis. These are thin-walled rounded cells with numerous inter- 

 cellular spaces. These cells become more numerous at the point of 

 formation of a leaf-trace, and adjoining the gap where the leaf-trace has 

 departed. 



The first appearance of the leaf-trace is made apparent by the thinning 

 down of the ring on one side of the solenostele (Fig 1, 2). This thin 

 portion breaks away, first on one side and then on the other, to form an 

 individual horse-shoe-shaped leaf-trace (Fig. 1, 4). The further behaviour 

 of the leaf-trace will be considered later. 



In the specimen investigated, which was of fairly advanced age, the gap 

 left by the formation of the lowest leaf is considerably longer than any of the 

 succeeding ones. It gradually closes down (Fig. 1, 6), and at the same time a 

 second leaf-trace is forming on the opposite side of the stele. The second 

 leaf-gap is formed just as the first closes, thus giving rise to a very simple 

 dictyosteles lightly removed from the solenostelic state. After the formation 

 of the third leaf-trace the gaps were found to overlap considerably (Fig. 1, 1 1), 

 and so dictyostely is well established. Sometimes in the mature stem, 

 however, there may be reversion r.o the solenostelic state. 



"We see, therefore, that while the stele of the adult Taenitis is a radial 

 dictyostele, it is a very simple one, not far removed from solenostely, to 

 which it has been seen occasionally to revert. The position of the protoxylem 

 elements is not recognizable in the mature stem. 



2t2 



