Fungi: Their Nature and Uses

by M. C. Cooke

Fig. 83.—Germinating pseudospore (b) of Melampsora betulina (Tulasne).

In Melampsora the summer spores are of the Lecythea type, and were included in that genus till their relation with Melampsora was clearly made out. The winter spores are in solid pulvinules, and their fructification takes place towards the end of winter or in the spring. This phenomenon consists in the production of cylindrical tubes, which start from the upper extremity of the wedge-shaped spores, or more rarely from the base. These tubes are straight or twisted, simple or bifurcated, and each of them very soon emits four monosporous spicules, at the same time that they become septate. The sporules are in this instance globose.

Fig. 84.—Germinating pseudospore of Uromyce appendiculatus. (Tulasne.)

In Uromyces germination follows precisely the same type as that of the upper cell of Puccinia; in fact, Tulasne states that it is very difficult to say in what they differ from the Pucciniæ which are accidentally unilocular.

In Cystopus a more complex method prevails, which will be examined more closely hereafter.

Fig. 85.—Germinating pseudospore of Puccinia Moliniæ. (Tulasne.)

In Puccinia, as already observed when describing their structure, the pseudospores are two-celled. From the pores of each cell, which are near the central septum, springs a clavate tube, which attains two or three times the total length of the fruit, and of which the very obtuse extremity curves more or less in the manner of a crozier.[G] This tube, making a perfectly uncoloured transparent membrane, is filled with a granular and very pale plastic matter at the expense of the generative cell, which is soon rendered vacant; then it gives rise to four spicules, usually on the same side, and at the summit of these produces a reniform cellule. The four sporules so engendered exhaust all the protoplasm at first contained in the generative cell, so that their united capacity proves to be evidently much insufficient to contain it, the more so as it leads to the belief that this matter undergoes as it condenses an elaboration which diminishes its size. In all cases the spicule originates before the sporule which it carries, and also attains its full length when the sporule appears. The form of the latter is at first globular, then ellipsoid, and more or less curved. All these phases of vegetation are accomplished in less than twelve hours, and if the spore is mature and ready for germination, it is sufficient to provoke it by keeping the pseudospores in a humid atmosphere. During this process the two cells do not separate, nor does one commence germination before the other, but both simultaneously. When the sporules are produced, the protospore, somewhat analogous to a prothallus, has performed its functions and decays. Towards the time of the falling of the sporules they are nearly all divided into four unequal cells by transverse and parallel septa. These sporules in time produce, from any point on their surface, a filament, which reproduces a new sporule, resembling the first, but generally smaller. This sporule of the second generation ordinarily detaches itself from its support before germinating.