1913] HOLM—PHRYMA LEPTOSTACHYA 313 
there are two thin-walled, parenchymatic strata between the 
endodermis (End) and the leptome (ZL), interspersed with stereids, 
and these two strata evidently represent what various authors have 
interpreted as a heterogeneous pericycle. Still another structure 
of this same pericycle may be observed in the oldest internodes of 
the inflorescence, that is to say, when the fruits have matured ; in 
these there is a very distinct sheath of two layers of stereids sur- 
rounding the leptome, hence representing a homogeneous, in this 
case a purely stereomatic, pericycle. 
The stereids inside the endodermis are thus only visible in the 
old, subterranean internodes of the main stem, and in the oldest 
internodes of the inflorescence, when the fruits have matured. 
But in all the other internodes, whether of seedlings or of mature 
plants, there is no pericyclic stereome, and barely any indication of 
a parenchymatic pericycle either. Moreover, the origin of the 
secondary mestome strands in Phryma cannot be attributed to the 
activity of a pericycle, but, as has been demonstrated, these sec- 
ondary strands of leptome and thick-walled libriform arise from 
the meristematic, peripheral strata of the primary parenchymatic 
(medullary) rays. 
Inasmuch as the origin of the secondary mestome strands, or, 
to be more exact, the interfascicular strands, seems to be different 
when we compare a number of dicotyledonous, especially herba- 
ceous, stems, it might be appropriate to present a brief abstract of 
the history of the pericycle. The term “‘pericycle” was proposed 
y VAN TikcHEM’ and applied to the parenchyma, of one or 
several layers, which he found in the stem between the endodermis 
and the mestome strands, as well as in the roots between the endo- 
dermis and the outer face of the leptome, and between the endo- 
dermis and the protohadrome vessels. To the activity of the 
pericycle VAN TrecHem ascribed the origin of the interfascicular 
arches of cambium with the subsequent development of secondary 
mestome strands. Moror; in describing the pericycle in general, 
’ Sur quelques points de Panatomie des Cucurbitacées. Bull. Soc. Bot. France 
29: 280. 1882, 
® Recherches sur le péricycle ou couche péripherique du cylindre central chez les 
Phanérogames, Ann. Sci. Nat. Bot. VI. 20: 249. 1885 
