=648.= In trillium and in the pepper root we have seen that the parts of the flower in each apparent whorl are either of the same number as the leaves in a whorl, or some multiple of that number. This is true of a large number of other plants, but it is not true of all. A glance at the spring-beauty (Claytonia virginiana), and at the anemone (or Isopyrum biternatum, fig. 563) will serve to show that the number of the different members of the flower may vary. The trillium and the dentaria were selected as being good examples to study first, to make it very clear that the members of the flower are fundamentally leaf structures, or rather that they belong to the same series of members as do the leaves of the plant. =649. Synopsis of members of the sporophyte in angiosperms.= Higher plant. Sporophyte phase {Root. {Foliage leaves. (or modern {Shoot. {Stem. {Perianth leaves. } phase). { Leaf. {Spore-bearing leaves } { with sporangia. } Flower. {(Sporangia sometimes } { on shoot.) } CHAPTER XXXVI. GAMETOPHYTE AND SPOROPHYTE OF ANGIOSPERMS. =650. Male prothallium of angiosperms.=—The first division which takes place in the nucleus of the pollen grain occurs, in the case of trillium and many others of the angiosperms, before the pollen grain is mature. In the case of some specimens of T. grandiflorum in which the pollen was formed during the month of October of the year before flowering, the division of the nucleus into two nuclei took place soon after the formation of the four cells from the mother cell. The nucleus divided in the young pollen grain is shown in fig. 385. After this takes place the wall of the pollen grain becomes stouter, and minute spiny projections are formed. [Illustration: Fig. 385. Nearly mature pollen grain of trillium. The smaller cell is the generative cell.] [Illustration: Fig. 386. Germinating spores (pollen grains) of peltandra; generative nucleus in one undivided, in other divided to form the two sperm nuclei; vegetative nucleus in each near the pollen grain.]