Brier ley .— The ‘ Endoconidia ’ of Thielavia basicola , Zopf. 489 
Faull, 1 working on Laboulbenia chaetophora and L. gyrinidarum , 
figures a delicate sheet of granules appearing across the diameter of the 
filament after the reconstitution of the nuclei. This becomes a definite 
cell-wall with a middle lamella. 
In the conidiophore of Thielavia the transverse wall is formed by 
the ingrowth of a constricting membrane some considerable time after 
the reconstitution of the nuclei. The walls in the chlamydospores of this 
fungus are formed in like manner. 
The phenomenon is apparently of cytoplasmic determination, and 
merely remotely or indirectly subject to nuclear control. 
The formation of a transverse wall by a constricting ring-like growth 
may be brought about in two ways. The inner laminae of the parent wall 
may infold in the manner described for certain Algae; 2 or, as occurs in 
Thielavia and the cases described by Olive, 3 by a progressive deposition of 
new cell-wall substance upon a localized surface of the parent wall. 
In its earliest stages the septum appears as a minutely granular, barely 
visible ring, becoming imperceptible at its ingrowing edge. With develop¬ 
ment its peripheral margin becomes more apparent, and a minute 
< -shaped mark may with difficulty be distinguished in the middle line 
of the parent wall opposite the diaphragm (PI. XXIII, Figs. 3, 3 a , 8). On 
the completion of the septum the wall rapidly assumes normal thickness and 
appearance (PL XXIII, Fig. 4). 
The >-shaped marking is in the line of the subsequent differentiation 
of sheath and inner wall and is probably a splitting apart of the laminae. 
The most careful microchemical analysis failed to reveal it as a substance. 
In certain cases investigated by Olive 4 the new wall invariably grows 
inwards, constricting a vacuole ; a protoplasmic bridge is later thrown across, 
and the completion of the membrane divides the vacuole into two portions. 
In Thielavia the new wall is invariably formed between vacuoles (PI. XXIII, 
Figs. 3 . 3 *)- 
In normal conidial development the formation of the transverse wall is 
complete; but occasionally in abnormal specimens a pore varying in 
diameter and admitting a wide protoplasmic strand is present (PI. XXIII, 
Figs. 10, 10 a). In rare instances the growth of the septum is such that 
it bears striking resemblance to the lamellose plugs of Codium (PL XXIII, 
Figs. 11, 11 a). 
It is interesting to note that in the transverse walls separating the 
chlamydospores, a single central pit is present. This, which is figured by 
1 Faull, J. H. : The Cytology of Laboulbenia chaetophora and L. gyrinidarum. Ann. of Bot., 
vol. xxvii, 1912. 
2 Brand, F.: Uber Membran, Scheidewande und Gelenke der Algengattung Cladophora . 
Festschr. der Deutsch. Bot. Ges., 1908, where the literature is cited. 
3 Olive, E. W.: loc. cit., 1906. 
4 Olive, E. W. : loc. cit., 1906. 
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