Fungi: Their Nature and Uses

by M. C. Cooke

Fig. 86.—Germinating pseudospore of Triphragmium ulmariæ (Tulasne.)

The pseudospores of Triphragmium ulmariæ have been seen in April germinating on old leaves of the meadowsweet which survived the winter, whilst at the same time new tufts of the spores were being developed on the leaves of the year. These fruits of the spring vegetation would not germinate the same year. Each cell in germination emits a long cylindrical filament, containing a brownish protoplasm, on which four spicules, bearing as many sporules, are generated.

Fig. 87.—Germinating pseudospore of Phragmidium bulbosum. (Tulasne.)

The germination of the black fruits of Phragmidium only appears to take place in the spring. It greatly resembles that in Puccinia, except that the filament is shorter, and the sporules are spherical and orange-coloured, instead of being kidney-shaped and pale. In the species found on the leaves of the common bramble, the filament emitted by each cell attains three or four times the length of the fruit. The granular orange protoplasm which fills it passes ere long into the sporules, which are engendered at the extremity of pointed spicules. After the long warty fruits are emptied of their contents they still seem as dark as before, but the pores which are pierced in the sides, through which the germinating filaments have proceeded, are more distinctly visible.

It will be observed that throughout all these allied genera of Uromyces, Puccinia, Triphragmium, and Phragmidium the same type of germination prevails, which confirms the accuracy of their classification together, and renders still less probable the supposed affinity of Phragmidium with Sporidesmium, which was at one time held by very astute mycologists, but which is now abandoned. This study of germination leads also to a very definite conclusion with regard to the genus Uromyces—that it is much more closely related to Puccinia and its immediate allies than to other unicellular Uredines.

Fig. 88.—Germinating pseudospores of Podisoma Juniperi. (Tulasne)

The germination of the pseudospores of the gelatinous Uredines of the genus Podisoma was studied by Tulasne.[H] These pretended spores, he writes, are formed of two large conical cells, opposed by their base and easily separating. They vary in length. The membrane of which they are formed is thin and completely colourless in most of them, though much thicker and coloured brown in others. It is principally the spores with thin membranes that emit from near the middle very obtuse tubes, into which by degrees, as they elongate, the contents of the parent utricles pass. Each of the two cells of the supposed spore may originate near its base four of these tubes, opposed to each other at their point of origin, and their subsequent direction; but it is rather rare for eight tubes, two by two, to decussate from the same spore or basidium. Usually there are only two or three which are completely developed, and these tend together towards the surface of the fungus, which they pass, and expand at liberty in the air. The tubes generally become thicker by degrees as they elongate, some only slightly exceeding the length of the protospores. Others attain three or four times that length, according to the greater or less distance between the protospore and the surface of the plant. In the longest tubes it is easy to observe how the colouring matter passes to their outer extremity, leaving the portion nearest to the parent cell colourless and lifeless. When nearly attaining their ultimate dimensions, all the tubes are divided towards their outer extremity by transverse septa into unequal cells; then simple and solitary processes, of variable length and form, but attenuated upwards, proceed from each segment of the initial tube, and produce at their extremity an oval spore (teleutospore, Tul.), which is slightly curved and unilocular. These spores absorb all the orange endochrome from the original tubes. They appear in immense numbers on the surface of the fungus, and when detached from their spicules fall upon the ground or on any object which may be beneath them. So freely are they deposited that they may be collected on paper, or a slip of glass, like a fine gold-coloured powder. Again, these secondary spores (teleutospores) are capable of germination, and many of them will be found to have germinated on the surface of the Podisoma whence they originated. The germ filament which they produce springs habitually from the side, at a short distance from the hilum, which indicates the point of attachment to the original spicule. These filaments will attain to from fifteen to twenty times the diameter of the spore in length before branching, and are in themselves exceedingly delicate. The tubes which issue from the primary spores (protospores, Tul.) are not always simple, but sometimes forked; and the cells which are ultimately formed at their extremities, though producing filiform processes, do not always generate secondary spores (teleutospores) at their apices. This mode of germination, it will be seen, resembles greatly that which takes place in Puccinia.