662 
Journal of Agricultural Research 
Vol. XXIV, No. 8 
usually near the ostiole but on the lower portion of the wall. They 
(PL 3, Ca) differ from the sporophores (PL 3, Cb, Cc) usually produced in 
large numbers on the upper surface of the fruiting body in spring, in 
being dark olivaceous rather than of a brown color, in being more closely 
septate, and in tapering toward the tip to about one-half their basal 
diameter. Although material of Pyrenophora tritici-repentis and P. 
bromi collected near Madison, Wis., in the spring of 1919 and 1920, 
showed asci and ascospores in excellent condition, the development of 
corresponding structures in P. teres did not go beyond a more or less 
abortive stage. In most instances the asci remained small; if ascospores 
were delimited, they usually failed to grow to normal dimensions, and 
frequently showed no cross walls. Plate 3, D represents approximately 
the least abnormal conditions found in the season of 1920, showing each 
of the asci with several obviously normal spores, the remainder being 
either more or less misshapen, or having one or several or all of the 
segments collapsed. The space in the interior of the imperfectly devel¬ 
oped fruiting body not occupied by asci, is filled with colorless vertically 
oriented, more or less filamentous pseudoparenchyma. As has been 
indicated in another connection, the failure of the asci to develop normally 
may be attributed to the advent of weather conditions in the spring 
encouraging the production of the numerous conidiophores (PL 3, B), 
the initiation of which appears to involve a cessation in the development 
of the internal parts of the perithecium. As abundant moisture and a 
relatively high temperature appear to favor the conidial stage, it is not 
illogical to expect fibat a long protracted period of cold, dry weather in 
spring might result in the production of more nearly normal asci. 
Judging from the more satisfactory material examined, the asci of 
Pyrenophora teres are subcylindrical throughout most of their length, 
the proximal portion tapering toward the short stipitate base, and the 
wall of the apical end modified by a ring-like thickening. They measure 
30 to 36 by 220 to 250 fif and contain 8 spores in distichous arrangement. 
Normal specimens of the latter are light brown in color; measure approxi¬ 
mately 18 to 22 by 52 to 60 II; and show three transverse septa associated 
with perceptible and often pronounced constrictions. One or both 
middle segments may, in addition, be divided by a longitudinal wall. 
The protoplasmic contents appear more or less granular and vacuolate. 
Germination takes place promptly when the spores are mounted in water, 
in a manner entirely similar to Aat of the two related ascigerous forms 
discussed in this paper. 
It is difficult to estimate the measure of importance to be attributed 
to the ascospores and conidia developed by the perithecia in reestab¬ 
lishing the fungus at the beginning of successive seasons. The abundance 
of these fructifications, however, indicates that they constitute a source 
of inoculum that ought not bo be overlooked, and certainly provides an 
additional reason for crop rotation, or such sanitary measures as turning 
under or otherwise disposing of the stubble of the preceding season. 
Most of the investigations relating to the control of netblotch have been 
carried out as subsidiary to control studies of the more destructive 
diseases affecting barley, particularly stripe, loose and covered smuts 
(Ustilago nuda and U. hordei), and spotblotch. In general, the seed 
treatments effective against stripe and spotblotch have also been found 
to reduce materially the number of primary infections of netblotch. 
Nevertheless the literature does not seem to indicate any treatment for 
the disease quite equalling in efficacy, for example, the various formajfle- 
