. Lessons with plants. Suggestions for seeing and interpreting some of the common forms of vegetation. travel in the wind ? Dodandelion plants vary much in size and shape of leaves (compareFig. 172) ? Is the variation associated with vigor of plant, richnessand moisture of soil, or other conditions ? At what seasons aredandelions most abundant ? Do they ever bloom in fall or winter ?How long does a dandelion plant live ? Upon what kind of soildoes it thrive best ? XXXIII. THE COMPOSITOUS TRIBES 201. A rudbeckia, or yellow ox-eye daisy^ is acommon plant in pastures and meadows. It hasrough and
. Lessons with plants. Suggestions for seeing and interpreting some of the common forms of vegetation. travel in the wind ? Dodandelion plants vary much in size and shape of leaves (compareFig. 172) ? Is the variation associated with vigor of plant, richnessand moisture of soil, or other conditions ? At what seasons aredandelions most abundant ? Do they ever bloom in fall or winter ?How long does a dandelion plant live ? Upon what kind of soildoes it thrive best ? XXXIII. THE COMPOSITOUS TRIBES 201. A rudbeckia, or yellow ox-eye daisy^ is acommon plant in pastures and meadows. It hasrough and hairy stems and leaves. A flower ofit is shown in Fig. 173. The central part of theflower is high and cone-shaped, and a cross-sectionof it shows that the receptacle, e, is really amuch-shortened stem, with flowers along its other words, the receptacle in compositousflowers is the rachis of a condensed spike, and M 178 JjJUSSON^S WITS PLANTS is, therefore, unlike the receptacle of single flowers. 202. This flower-head also differs greatly from that of the dandelion, because it has a black-. FlG. ox-eye or rudbeckia. brown center and a yellow corolla-like rim, green and hairy involucre is readily distin-guished below, at *. Dissecting the flower, theseouter yellow petal-like bodies are found to be likethe figure at A. This suggests one of tne floretsof the dandelion, except that it has no essential THE COMPOSITOUS TRIBES 179 organs. The tube-like base, and especially theabortive ovary or seed, show that it is morpho-logically a flower, but it is neutral! That is, thereare some members which bear every evidence ofbeing modified flowers which have no stamens orpistils and which, therefore, are functionally notflowers at all; but they may answer the purposeof the petals of simple flowers in attracting insects. 202a. Neutral flowers are frequent in the composites. Examinethe sunflowers, cosmos, and coreopsis (or calliopsis of gardens). Inother kinds of plant
Size: 1498px × 1669px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorbai, bookcentury1900, bookdecade1900, booksubjectbotany
