similar circumscribed dead area surrounds those sori of P. annularis which are formed late in the year, and that it is by means of teleutospores contained in these sori that the fungus is reproduced in the following spring.

The localized mycelium of the acidiospores especially, has a powerful influence upon the chlorophyll, causing it to lose its green colour, and, as De Bary has pointed out with R. cancellata, making it disappear entirely. The affected tissue is found to contain an immense number of minute starch granules. To such an extent does the development of starch take place, that in the Himalayas the natives eat the hypertrophied stems of Urtica parvifolia, which are affected with c. urtica, on account of the abundant nutritive starchy material they contain. The hypertrophies are eaten just before the acidia open, and are said to resemble cucumber in flavour. The affected places generally assume some tint of yellow or reddish yellow, more or less bright. In the Polygoneæ the spots are bright red or purplish (Æc. rumicis, Uredo bifrons). In other cases they are yellow, surrounded by a purplish or reddish border (Æc. zonale, behenis). In a few instances all colour is more or less discharged, and the spots appear whitish (Æc. albescens, leucospermum).

The mycelium of all species is by no means thus localized. With some Uredines, on the contrary, it pervades the whole plant with the exception of its rootsstem, leaves, petioles, peduncles, and the upper part of the root-stock. De Bary has shown that when the mycelium of a Uredine can be traced into the perennial parts of the host-plant, it is itself perennial; thus with

* De Bary, "Brandpilze," p. 73.

+ Surgeon-Major A. Barclay, "On Ecidium Urtica," " Scientific Memoirs by Medical Officers of the Indian Army" (1887), p. 2.

De Bary, "Neue Untersuchungen über Uredineen " (1865), pp. 20, 21.

Endophyllum euphorbia it is found more particularly in the pith and in the inner parenchyma of the bark of the affected plants. In plants of Anemone nemorosa, it may be found in the leaves, stems, and vascular bundles of the upper part of the rhizome, as is likewise the case with the host-plants bearing Uredo suaveolens and Æc. tragopogonis.

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CHAPTER III.

SPERMOGONIA AND THE SO-CALLED SPERMATIA.

THESE bodies are produced by the mycelium, which arises directly from the entrance of the germ-tube of a promycelial spore, or from a perennial mycelium permeating the tissues of the host-plant.

The hyphae which are destined to form a spermogonium become interwoven into an inextricable network in the subepidermal tissues of the host-plant. They pass for the most part between the cells, and are found more frequently septate where a spore-bed is about to be formed than when they are encountered elsewhere in the tissues of the hostplant. Their contents are watery and transparent. From this tangled mesh, immediately beneath the epidermis, are given off a great number of branches of much smaller diameter, as a rule about 2 or 3μ. The general direction of these finer branches is towards the epidermis. They incline towards a central point, however, and so come together, forming a pyriform or subglobose body, the upper part of which is covered only by the cuticle of the hostplant. This body soon assumes a pyriform or flask-shaped contour (Plate I. Fig. 3). The neck of the flask bursts through the epidermis as a minute conical point, which can be seen to consist of a vast number of straight hyphæ, parallel to one another in the main, but all sloping upwards, converging

to the apex of the cone. The outer walls of this body are embedded between the cells of the host-plant, and are likewise composed of similar fine hyphæ, placed side by side. A section of the spermogonium at this time shows its interior to consist of similar converging parallel hyphæ. Very soon those hypha which constitute the emerging apex separate from one another, so as to appear as a brush of stiff hair like bodies (paraphyses); in the centre of this brush is a minute canal, which passes downward to the interior of the body of the spermogonium (Plate I. Fig. 4). The apices of those converging hyphæ which occupy the lower part of the spermogonial interior, are now seen to be surmounted by very minute irregularly oval or rounded bodies (Plate I. Fig. 5)-the so-called spermatia. These spermatia vary in size, not only in the different species, but also in the same spermogonium. In those I have examined, they were from 5 to 8μ long, and 3 or 4 or even 6μ wide. Tulasne gives the measurement of the spermatia of Triphragmium ulmaria and Puccinia fusca as from 5 to 6μ long, while those of most the Ecidia and of Caoma pingue and C. ribesii are rarely more than 4u long. The spermatia are produced in linear series from the apices of the hypha (sterigmata), which fill the interior of the spermogonium. These are held together by a viscid, gelatinous substance, which at first fills the bottom of the canal; but as more spermatia are produced, gradually the whole canal becomes full, and eventually the mass oozes out at its upper end in the form of a globule. The cause of the expulsion of the spermogonial mass is, as De Bary+ has shown, the imbibition of moisture, which causes the investing gelatinous material to swell. As the spermogonium advances in maturity, its flask-like neck opens out, so that, instead * Tulasne, "2 Mémoire," p. 118. † De Bary, "Brandpilze," p. 60.

*

of resembling a flask with a bristly mouth, it comes to be a cup-shaped depression on the surface of the leaf, surrounded by a hedge of stiff bristles (Plate I. Fig. 4). The function of these bristly paraphyses appears to be that of preventing the exuded mass of spermatia and jelly from being bodily washed off the surface of the leaf by rain. This is the more necessary, because it is during wet weather, as we have seen, that the spermatia, from the imbibition of moisture by their investing jelly, are brought to the surface of the leaf at all. The paraphyses occur with all spermogonia except those of the Phragmidia.

*

Whatever their functions may be, whether as a sporeform or as spermatia properly so called, it is obvious that, by being held together by a viscid substance, their chance of dissemination by currents of air, etc., is but small. To a certain extent their diffusion over a limited area might take place in very wet weather. Ráthay has, however, shown that the spermatial mass contains a certain amount of some saccharine material mixed with it-a substance which has the power of reducing Fehling's solution; and further, that, as a matter of fact, insects do visit spermogonia for the sake of this saccharine matter, and are thereby unwittingly the agents for the distribution of the spermatia. Of this latter point, he obtained actual demonstration in the following manner. He had standing upon his windowsill some plants of Euphorbia amygdaloides, upon which a large number of spermogonia of Endophyllum euphorbia were in the act of exuding their contents. One day, as he approached the window in question, he noticed some flies, which were busy upon these leaves, fly away from the leaves and alight upon the window pane. Closer scrutiny showed that the flies had left their wet footmarks upon the Ráthay, "Untersuchungen über die Spermogonien der Rostpilze." Wien:

1882.