=641. Corolla.=—Next above the calyx is a whorl of white or pinkish members, in Trillium grandiflorum, which are also leaf-like in form, and broader than the sepals, being usually somewhat broader at the free end. These make up what is the _corolla_ in the higher plants, and each member of the corolla is a _petal_. But while they are parts of the flower, and are not green, their form and position would suggest that they also belong to the leaf series. [Illustration: Fig. 378. Trillium grandiflorum.] =642. Andrœcium.=—Within and above the insertion of the corolla is found another tier, or whorl, of members which do not at first sight resemble leaves in form. They are known in the higher plants as _stamens_. As seen in fig. 379 each stamen possesses a stalk (= filament), and extending along on either side for the greater part of the length are four ridges, two on each side. This part of the stamen is the _anther_, and the ridges form the anther sacs, or lobes. Soon after the flower is opened, these anther sacs open also by a split in the wall along the edge of the ridge. At this time we see quantities of yellowish powder or dust escaping from the ruptured anther locules. If we place some of this under the microscope we see that it is made up of minute bodies which resemble spores; they are rounded in form, and the outer wall is spiny. They are in fact spores, the microspores of the trillium, and here, as in the gymnosperms, are better known as _pollen_. [Illustration: Fig. 379. Sepal, petal, stamen, and pistil of Trillium grandiflorum.] [Illustration: Fig. 380. Trillium grandiflorum, with the compound pistil expanded into three leaf-like members. At the right these three are shown in detail.] =643. The stamen a sporophyll.=—Since these pollen grains are the spores, we would infer, from what we have learned of the ferns and gymnosperms, that this member of the flower which bears them is a sporophyll; and this is the case. It is in fact what is called the _microsporophyll_. Then we see also that the anther sacs, since they enclose the spores, would be the sporangia (microsporangia). From this it is now quite clear that the stamens belong also to the leaf series. They are just six in number, twice the number found in a whorl of leaves, or sepals, or corolla. It is believed, therefore, that there are two whorls of stamens in the flower of trillium.