1913] HOLM—PHRYMA LEPTOSTACHYA 311 
primordial, spiral and annular. An endoxyle (fig. 7) is quite well 
represented, especially in the subterranean internodes as well as in 
the swollen portion of the upper internodes. Between these pri- 
mary mestome strands in the various stem portions (of seedlings and 
mature individuals) there are several strata of secondary mestome, 
that is, leptome and thick-walled libriform, but with no vessels.° 
It is interesting to trace the origin of these tissues, the leptome 
and the libriform, and it might be stated at once that only the 
leptome develops from the pericycle, and only sometimes. What 
seems to be more important for the development of these secondary 
tissues in Phryma is undoubtedly the peripheral portion of the pri- 
mary parenchymatic or medullary rays, which is still meristematic 
and capable of producing new tissues. Fig. 8 shows a small part 
of the interfascicular tissue, taken from the base of a very young 
lateral inflorescence, and here may be seen the thin-walled, large- 
celled endodermis (End), inside of which are small strands of young 
leptome, some perhaps developed from the pericycle itself, while 
others have developed in the tissue inside, the primary parenchy- 
matic ray. As may be readily seen from this drawing, there is no 
real indication of any definite sheath such as a pericycle of one or 
of several strata. There is, on’ the other hand, a very distinct 
meristematic tissue in the periphery of the primary parenchymatic 
(medullary) ray giving rise to leptome, sometimes bordering on the 
endodermis, or some distance from it. In other words, this par- 
ticular section (fig. 8) does not show the derivation of the secondary 
leptome from the pericycle alone, but from a meristematic tissue 
within the endodermis, a tissue of several homogeneous strata. 
* Santo (Bot. Zeit. 1863:10r) proposed the term “libriform”: “einfache (d. h. 
ungetheilte) bastartige Holzfasern oder Holzzellen, fibrae sive cellulae libriformes 
simplices. Um einen kurzen Ausdruck zu gewinnen werde ich dieselben Libriform- 
fasern, und das daraus bestehende Gewebe Libriform nennen.” HABERLANDT 
(Physiol. Pflanzenanat. 1896:138), however, calls attention to the fact that the dis- 
tinction between libriform and stereome depends upon the different location of these 
those outside. However, from a physiological point of view, it seems unimportant 
whether such mechanical cells are located inside or outside the cambial zone, hence 
the distinction between libriform and stereome is not well founded except topo- 
graphically, 
