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growing in almost straight lines towards the centre. When maturity is reached the spermogonium opens at the top, and the contents burst through the epidermis of the barberry leaf, as shown. At the time of bursting, the little dark central mass turns up towards the burst point, and the growth of the spermogone threads is continued through the orifice, as shown at HH. The septate spermogone threads, after they have reached the air, break up into

[graphic][subsumed][subsumed][subsumed][subsumed][merged small][merged small][merged small]

Section through a Spermogonium of Ecidium Berberidis, Pers.

Enlarged 300 diameters.

extremely small granules, and these granules are the spermatia of botanists. They are supposed to be little grains belonging to a male organism, roughly answering to the pollen of flowering plants. Most of the illustrations of Ecidium spermogonia hitherto published are incorrect. After the Ecidium cups and spermogonia are once formed, most of the mycelium amongst the cells of the leaf,

from which the cups and spermogonia arose, breaks up into the finest conceivable dust, or dissolves away, and so is lost to sight.

A single Æcidium spore is enlarged to 1000 diameters at Fig. 86. To the spore are attached four of the so-called

[blocks in formation]

Germinating spore of Acidium Berberidis, Pers:
Enlarged 1000 diameters.

spermatia from the spermogones, just as one commonly sees pollen-grains agglutinated on to a stigma.

The spores germinate rather sluggishly on damp surfaces, but when seen in a state of germination a mycelial thread is protruded in a convolute fashion from one of about six privileged or weak points on the surface of the spore. Into the mycelial thread the vital material from the spore is poured.

The tardy germination of the spores seems to indicate that they are of the nature of resting-spores, and therefore able, under suitable conditions, of resting for a prolonged time. It is generally believed that the spores arise from male and female elements, and these facts indicate to some observers that the cycle of the Ecidium is complete in the production of these spores, or that no other spores are likely to exist unless simple conidia or bud spores, as opposed to resting or sexually-produced spores.

Of late considerable attention has been directed to the fact of the occurrence of Æcidium Berberidis, Pers., on the more ornamental species of barberry of our gardens and shrubberies, and especially its growth upon Mahonia Aquifolium, Lindl. The rare occurrence of the parasite

upon other barberries than the wild barberry of Britain has long been well known. A short paper from the pen of Mr. Charles B. Plowright, M.R.C.S., has been published in the Proceedings of the Royal Society, No. 228, 1883. In this paper Mr. Plowright considers he has proved by experiment that the Ecidium upon Mahonia is one condition of the summer mildew of corn, Puccinia graminis, Pers. Mr. Plowright kindly furnished us with numerous examples of Mahonia berries on which the Ecidium was growing, not only upon the exterior of the berries, but sometimes upon the seeds exposed in berries burst by the

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Berries of Mahonia Aquifolium, Lindl., invaded by Ecidium Berberidis, Pers. Enlarged 5 diameters.

growth of the fungus. Doubtlessly the Ecidium cups grew on the seeds after the berries were burst. Two Mahonia berries badly infested with the Ecidium are illustrated at Fig. 87, enlarged five diameters. The presence of the fungus, as is usual, causes hypertrophied or greatly swollen places on the affected part. We shall refer to Mr. Plowright's communication further on; in the meantime we point out that the parasite sometimes occurs on the leaves and petioles, as well as the berries of Mahonias and the other ornamental species of garden barberries.

Here we come to a halt similar to the one we came to at the conclusion of the description of Puccinia graminis, Pers. Some botanists believe that Æcidium Berberidis, Pers., is probably complete in itself, others state that the Ecidium spores will not enter the organs of transpiration of barberry leaves, but will only enter the stomata of grasses, and that then they produce, not an Æcidium, but a Uredo, viz. Uredo linearis, Pers., the first stage of the fungus of the summer mildew of corn,—Puccinia graminis, Pers. It will be remembered that a similar phenomenon was said to hold good with the fungus of spring mildew of corn and the fungus of borage blight.

We will now impartially review the evidence brought forward on both sides of this disputed question, withholding nothing—as far as our knowledge goes for or against the alleged connection of Puccinia and Ecidium.

CHAPTER XXV.

THE POSSIBLE CONNECTION OF THE FUNGUS OF CORN MILDEW AND THE FUNGUS OF BARBERRY BLIGHT.

In the following review of the evidence for and against the connection of the fungi found under the genera Puccinia and Ecidium, it will be understood that the remarks made in reference to the fungus of the summer rust and mildew of corn, with its supposed Æcidium condition on barberry bushes, applies also to the spring rust and mildew and its supposed Acidium on members of the Borage family. In fact, the following notes apply to every instance where there is a supposed connection between Puccinia and its allied genera on the one hand, with Ecidium and its allied genera on the other.

First we will give a brief account of the popular belief which is said to have existed amongst rustics in old times, then we will give the evidence brought forward by some men of science as supposed proofs of an actual connection of corn mildews with the blights of barberry and borage; and, lastly, we will state the reasons why other men of science in some instances reject the evidence of the supposed connection, and in other cases consider the connection as unproven. As each of these branches of the subject are reviewed we will state how our mind has been impressed by the statements. The readers of this chapter may then form their own opinion as to the value of the facts as well as of the deductions which have been either reasonably or unreasonably drawn from them.

The first we hear in regard to the connection of corn

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