638.
TABLE SHOWING HOMOLOGIES OF SPOROPHYTE
AND GAMETOPHYTE IN THE PINE.
| Terms Corresponding to those used in Pteridophytes. | Common Terms. | |||
|---|---|---|---|---|
| Sporophyte | = | Pine tree. | ||
| Spore-bearing part | = | Male and female cones. | ||
| Sporophyte | Microsporophyll | = | Stamen. | |
| Microsporangium | = | Pollen sac. | ||
| Male gametophyte | Microspore | = | Pollen grain. | |
| Mature microspore is rudimentary male prothallium | = | Mature pollen grain. | ||
| with rudimentary antheridium | ||||
| Large cell (part of antheridium wall?) | = | Vegetative cell of pollen grain. | ||
| Antheridium cell | = | Small cell of pollen | ||
| Antheridium cell divides to form stalk cell and | = | Generative cell. | ||
| central cell of antheridium (male sexual organ) | ||||
| Central cell of antheridium divides to form | = | Paternal cells, or | ||
| two sperm cells | generative cells. | |||
| Sporophyte | Macrosporophyll | = | Ovuliferous scale (cover scale | |
| and carpellary outgrowth); or | ||||
| three carpels united into | ||||
| ovuliferous scale, the central one | ||||
| sterile (in axil of cover scale). | ||||
| Macrosporangium covered by integument | = | Nucellus covered by | ||
| by integument | integument = ovule. | |||
| Female gametophyte | Macrospore (remains in sporangium) | = | Large cell in center of nucellus | |
| which develops embryo sac and | ||||
| endosperm (remains in nucellus). | ||||
| Female prothallium (in sporangium) | = | Endosperm, in nucellus. | ||
| Archegonia (female sexual organs) | = | Corpuscula, in endosperm. | ||
| Egg | = | Maternal cell, or germ cell. | ||
| Young sporophyte | Egg (fertilized) | = | Germ cell. | |
| Young sporophyte | = | Pine embryo in nucellus | ||
| and integument. | ||||
| Young sporophyte | = | Embryo | Seed. | |
| In remains of gametophyte | = | Endosperm | ||
| And sporangium | = | Nucellus | ||
| Surrounded by new growth of old sporophyte | = | Integument | ||
[CHAPTER XXXV.]
MORPHOLOGY OF THE ANGIOSPERMS:
TRILLIUM; DENTARIA.
Trillium.
639. General appearance.—As one of the plants to illustrate this group we may take the wake-robin, as it is sometimes called, or trillium. There are several species of this genus in the United States; the commonest one in the eastern part is the “white wake-robin” (Trillium grandiflorum). This occurs in or near the woods. A picture of the plant is shown in [fig. 378]. There is a thick, fleshy, underground stem, or rhizome as it is usually called. This rhizome is perennial, and is marked by ridges and scars. The roots are quite stout and possess coarse wrinkles. From the growing end of the rhizome each year the leafy, flowering stem arises. This is 20-30cm (8-12 inches) in height. Near the upper end is a whorl of three ovate leaves, and from the center of this rosette rises the flower stalk, bearing the flower at its summit.
640. Parts of the flower. Calyx.—Now if we examine the flower we see that there are several leaf-like structures. These are arranged also in threes just as are the leaves. First there is a whorl of three, pointed, lanceolate, green, leaf-like members, which make up the calyx in the higher plants, and the parts of the calyx are sepals, that is, each leaf-like member is a sepal. But while the sepals are part of the flower, so called, we easily recognize them as belonging to the leaf series.
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.