314 BOTANICAL GAZETTE [OCTOBER 
calls attention to the fact that while the pericycle is always present 
in roots (frequently called pericambium), it is not always to be 
found in stems; on the other hand, he agrees with VAN TIEGHEM 
in respect to the function of the pericycle. GERARD? and HERAIL” 
question the assertion of VAN TIEGHEM in respect to the function 
of the pericycle in stems, and describe a number of cases where 
the interfascicular tissues develop independently of the pericycle. 
Moreover, Hérart describes some cases of secondary mestome 
developing in the pith (Melastomaceae and Campanulaceae). 
Finally, HABERLANDT™ makes no use of the term pericycle in stems, 
but only in roots; and in reference to the secondary increase in 
stems, he speaks of a “cambium ring”’ being the direct product of 
a “procambium,” and of an interfascicular cambium owing its 
existence to a meristem in the primary parenchymatic (medullary) 
rays. . 
In Phryma the presence of stereids is actually the only distinc 
indication of a pericycle, as scattered strands in the pseudo- 
rhizome, or as a closed sheath in parts of the inflorescence. The 
origin of these stereids I have been unable to detect, but it may be 
sought in the outermost layers of the leptome, and rather so than 
in any particular tissue, such as a pericycle for instance, inside the 
endodermis. ‘Therefore, I am most inclined to believe that Phryma 
lacks a pericycle; in any case, the interfascicular tissues appear to 
develop independently of it, especially the libriform. However, 
the term “‘pericyclic” is quite convenient to use when describing 
the stereome strands between the endodermis and the leptome, 
because they are “‘peri” “cyclic,” even if we do not always regard 
them as representing a pericycle as defined by VAN TIEGHEM, that 
is, a constant sheath of parenchyma from which the secondary 
tissues arise. It seems also worth while to compare this pericycle 
of stems with the well known pericambium of roots, where } 
Tepresents the peripheral tissue of the stele, and typically so. 
Returning to the stem of Phryma, the central part of the stele 
» Passage de la racine a la tige. Ann. Sci. Nat. Bot. VI. 15:1881. 
* Recherches sur l’anatomie comparée de la tige des Dicotylédones. Ann. Sc. 
Nat. Bot. VII. 2:188s. 
* Physiologische Pflanzenanatomie. Leipzig. 1896. 

