SECTION OF VEGETABLE PATHOLOGY. 367 
able to the parasite. Those which escape early in the season are apt 
to succumb before fall if the other roses in the vicinity are diseased. 
The effect of the disease upon the leAf is soon apparent by its turn- 
ing yellow in places, and sometimes by a yellow band outside the 
black spot. When cold weather approaches the leaves that are dis- 
eased are the first to turn yellow. During the autumn the yellow 
color is apt to appear at the apex of the leaflets, whence it spreads 
downward and is succeeded by brown. A leaf with a green base and 
brown tip with a yellow band between is very characteristic of this 
disease. Premature fall of the leaves is another effect of this para- 
site. Diseased leaves may fall before they turn yellow, and plants 
attacked by the fungus generally have a partly defoliated appear- 
ance. 
It is evident that we have here a case in which the effect of the 
fungus is not confined to the area it actually occupies. Its growth 
does not extend over all those parts of the leaf which turn yellow, 
nor can any mycelium be found at the base of the petiole when the 
leaf falls before its time. It seems that the interference with assim- 
ilation which must result over the diseased areas so affects the entire 
leaf as to destroy its vitality. If the autumn is long and pleasant 
the plant is apt to exhaust itself by putting out new leaves, which 
are destroyed by frost before they can be of any service. 
The fungus is very hardy and does not depend to any great extent 
upon climatic conditions for its development, but like other diseases 
of this kind it proves most troublesome in a moist and warm environ- 
ment. 
Roses kept under cover are better protected from infection, and 
are consequently more free from the disease. This explains why tea 
roses and others that are kept in greenhouses over winter are not so 
badly affected as those in open grounds. The truth is, probably, 
that the disease has a long period of incubation before it is visible, 
and before this period is over for roses that have been potted the 
season is far advanced and they do not have time to get badly dis- 
eased before they are potted again. 
(ce) BOTANICAL CHARACTERS. 
The pane, as it is known on the rose, is probably but one stage 
in the life history of the fungus. From its analogies it is classed 
with the spheeriaceous fungi, althgugh so far as recorded no peri- 
thecia have been observed in this species. But in other species 
similar in habit to this one, perithecia-like forms, more accurately 
known as pycnidia, occur. . 
Myceliwm.—The mycelium is composed of two distinct parts, one 
situated between the cuticle and epidermis (Plate IX, Fig. 2, b), and 
the other penetrating the leaf tissues. The former is apparently 
superficial (Plate VIII, Fig. 2), as it shows through the transparent 
cuticle. It is composed of branched septate hyphe that radiate from 
a center and lie side by side in strands of from one to eight (Plate 
VIII, Figs. 2 and 3). When a hypha branches it may run along 
parallel to the main thread or may bend off at an acute angle and 
form an independent strand (Plate VIII, Fig. 3). Other mycelial fil- 
aments branch off from the under surface of this superficial layer 
and penetrate the leaf tissues, first entering the epidermal cells and 
sometimes nearly filling them with convolutions (Plate IX, Fig. 2). 
Hrom these it pushes between the palisade cells, and finally appears 
