. Foundations of botany. Fig. 266. — Fruits of Linden, with a Bract joinedto the Peduncle and forming a Wing. S78 FOUNDATIONS OF BOTANY The student should be able, from his own observations onthe falling fruits of some of the trees and other plants abovementioned, to answer such questions as the following : What is the use ofthe wing-like append-ages? of the tufts ofhairs ?f Which set of con- trivances seems to bethe more successful ofthe two in securingthis object? What particularplant of the ones avail-able for study seemsto have attained thisobject most perfectly ?What is one reasonwhy many
. Foundations of botany. Fig. 266. — Fruits of Linden, with a Bract joinedto the Peduncle and forming a Wing. S78 FOUNDATIONS OF BOTANY The student should be able, from his own observations onthe falling fruits of some of the trees and other plants abovementioned, to answer such questions as the following : What is the use ofthe wing-like append-ages? of the tufts ofhairs ?f Which set of con- trivances seems to bethe more successful ofthe two in securingthis object? What particularplant of the ones avail-able for study seemsto have attained thisobject most perfectly ?What is one reasonwhy many plants withtufted fruits, such asthe thistle and the dan-delion, are extremelytroublesome weeds? A few simple experi-ments, easily devisedby the student, mayhelp him to find an-swers to the questionsabove given.^. Fig. 267. — Winged Fruits of Thistle ; Winged Seedsof Milkweed. 448. Tumbleweeds. — Late in the autumn, fences, par-ticularly on prairie farms that are not carefully tilled, oftenserve as lodging-places for immense numbers of certaindried-up plants known as tumbleweeds. These blowabout over the level surface until the first snow falls and 1 See Kerner and Oliver, Vol. II, pp. 833-875; also Beals Seed Dispersal. HOW PLANTS ARE SCATTERED 379 even after that (Fig. 269), often traveling for many milesbefore they come to a stop, and rattling out seeds as theygo. Some of the commonest tumbleweeds are the Russianthistle (Fig. 268), the pigweed (Amarantus alhus., Fig. 269),the tickle-grass (Fig. 270), and a familiar pepper-grass{Lepidium). In order to make a successful tumbleweed, aplant must be pretty nearly globular in form when fullygrown and dried, must be tough and light, must break offnear the ground, and drop its seeds only a few at a timeas it travels. A single plantof Russian thi
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectplants, bookyear1901
