Some very curious details are observable in these cases of malformation, For instance, the Aecidium eta/mum first referred to causes the new shoots to differ in direction, duration and arrangement, and even shape of foliage leaves from the normal; and the shoots of Euphorbia infected with the aecidia of Uromyces Pisi depart so much from the normal in appearance that the attacked plants have been taken for a different species.
Gymnosporangium sabinae, one of the rusts (Uredineae) passes one stage of its life-history on living pear leaves, forming large raised spots or patches which are at first yellow but soon become red and are visible on both faces; on the lower face of each patch is a group of cluster-cups or aecidia containing spores which escape when ripe.
Similarly with the various types of conidial or oidial "fructifications," termed pycnidia, spermogonia, aecidia, &c. In the simplest of these cases - e.g.
Although in the forms without aecidia the two generations are not sharply marked off from one another, we may look up the generation with single nuclei in the cells as the gametophyte and that with conjugate nuclei as the sporophyte.
In due time the fungus, known as Aecidium Berberidis, appears on the barberry leaves in the form of small cluster-cups on aecidia, each of which is filled with chains of orange-coloured aecidiospores.