of P. Rubigo-vera, D.C., illustrated in Fig. 69, both enlarged 1000 diameters. The supporting stems of Puccinia graminis, Pers., are larger in proportion, and are accompanied by no paraphyses

in the sori.

To see the germination of the black Puccinia spores, old Puccinia invaded straw must be looked for in the spring months, and the Puccinia spores must be taken from a pustule with a small knife or needle, and placed in a film of water under a thin cover glass on a slide, and kept in moist air (to prevent evaporation) under a bell glass. Germination usually takes place, as in P. Rubigo-vera, D.C., by the protrusion of a thread from each of the two cells of the Puccinia spore, as illustrated at Fig. 81, enlarged 1000 diameters. These two threads, the first produced in the spring, are the pro-mycelium, or the first mycelium, of one end of the cycle springing from the "finishing spores" or teleutospores belonging to the other end. This pro-mycelium is seen at AA.

The

pro-mycelium proceeds to no great length, but after some

times attaining three or four times the length of the black

Teleutospores of Puccinia graminis, Pers., germinating in early summer. Enlarged 1000 diameters.

teleutospore belonging to the Puccinia, it usually coils round somewhat like a shepherd's crook, produces about

three stops, joints, or septa, as at B, C, D, and from each of the three separate pieces three fine branches arise, and these branches bear at their tops three irregular oval transparent, very pale amber-coloured spores, as illustrated at E, F, G. These spores are the third of the series. First we have Uredo, or rust spores; then Puccinia, or black mildew spores; last, spring or pro-mycelium spores.

Pro-mycelium spores germinate very readily in a film of water on glass, as illustrated at H, by the protrusion of a fine tube of mycelium.

In a state of nature the black Puccinia spores germinate upon straw, as it rots on the ground in the spring, and the minute ovoid pale lemon-coloured spores are carried about in the air in millions-that, too, in the springtime, when corn first becomes invaded, and when the first signs of summer rust or Uredo appear upon our cereals.

Judging by what is well known amongst other fungi, it would be perhaps reasonable to suppose that these little hyaline spores (particularly as they arise from specialised resting-spores) would reproduce the rust from which they were originally derived (and nothing else), if they came in contact with grasses. Many botanists believe this to be a fact; others say they do not, but, on the contrary, that the cycle of corn mildew is not complete with the production of these spores. Many observers believe that before the pro-mycelium spores can cause the rust of corn they must be nursed by a barberry bush; that the lemon coloured spores invariably refuse to effectually grow on the leaves of grasses, but when placed on the leaves of barberries they find themselves so thoroughly in a natural position that they do not, on germination (like the majority of fungus spores) gently follow the uneven surface of the leaf cells, and so quietly enter by the stomata; but the mycelium from the spores, it is said, sinks into the hard leaves of the barberry, through the cells of the epidermis (not between them) to the body of the leaf, and there,

having gone from a monocotyledonous plant to a dicotyledonous one, another fungus is produced of an apparently totally different character, named Æcidium Berberidis, Pers.

This is the fungus of barberry blight, described in the next chapter. Our comments on the possible connection of the barberry fungus with the fungus of summer mildew of corn is discussed farther on.

Puccinia graminis, D.C., has been recorded in Britain upon Phalaris arundinacea, L.; Phleum pratense, L.; Alopecurus pratensis, L.; A. fulvus, Sm.; Agrostis vulgaris, With.; A. alba, L.; Calamogrostis Epigejos, Roth.; Aira cæspitosa, L.; Avena sativa, L.; A. fatua, L.; A. pratensis, L.; A. flavescens, L.; A. elatior, L.; Holcus lanatus, L.; Poa annua, L.; P. nemoralis, L.; P. pratensis, L.; Molinia cærulea, Moench.; Dactylis glomerata, L.; Festuca gigantea, Vill.; F. spectabilis, Jan. ; F. tenella, Willd.; Bromus mollis, L.; B. tectorum, L.; Lolium perenne, L.; Triticum vulgare, Vill.; T. repens, L.; T. caninum, Huds.; Elymus arenarius, L.; E. glaucifolius, L.; Hordeum vulgare, L.; H. sylvaticum, Huds.; H. murinum, L.; H. distichum, L.; Egilops ovata, L.; Secale cereale, Walld.

CHAPTER XXIV.

BARBERRY BLIGHT.

Ecidium Berberidis, Pers.

THERE is perhaps no family of plants more free from fungi than the Berberidaceae, and in this fact the family greatly differs from the Graminea, on various members of which the fungi of spring and summer mildew of corn are so prevalent. It is also noteworthy that the Boraginaceæ, upon some members of the order, as already described, the supposed second condition of spring mildew of cornEcidium asperifolii, Pers., -occurs, are also free from the attacks of fungi to an extraordinary degree. Grasses are all badly infested with fungus parasites and epiphytes. The only important fungus peculiar to the barberry is the one named Æcidium Berberidis, Pers. The generic name Æcidium has been explained; the specific name Berberidis explains itself.

Ecidium Berberidis, Pers., is frequent on the common barberry, Berberis vulgaris, L. It also grows rarely on the more ornamental species of Berberis and on the Mahonias of our gardens.

At Fig. 82 is illustrated, natural size, a few leaves attached to a small fragment of a branch of the common barberry. The parasitic Æcidium almost invariably grows on the under surface of the leaves, as there shown, although it may be detected rarely on both sides, and indeed on every part of the plant. The Acidium growths are seen at AAA. The Æcidium clusters, of which there are ten in the illustration, are groups of little sulphur-coloured spots embedded in dark red, swollen, or hypertrophied