130 



THE FKCIT. 



[lesson 20. 



thin scales which fall off at the touch ; in the Sneezeweed, of about 

 five very thin scales, which look more like a calyx (Fig. 294) ; and 

 in the Tliistle, Aster, Sow-Thistle (Fig. 2&5), and hundreds of others, 

 it is cut up into a'tuft of fine bristles or hairs. This is called the 

 Pappus ; — a name which properly means the down like that of the 

 Thistle ; but it is applied to all these forms, 

 and to every other under which the limb of the 

 calyx of the " compound flowers " appears. In b;] 

 Lettuce, Dandelion (Fig. 296), and the like, ^'ft' 

 the achenium as it matures tapers upwards 

 into a slender beak, like a stalk to the pappus. 



SoO. A Utricle is the same as an achenium, but with a thin and 

 bladdery loose pericarp ; like that of the Goosefoot or Pigweed 

 (Fig. 297). When ripe it bursts open irregularly to 

 discharge the seed ; or sometimes it opens by a circular 

 line all round, the upper part falling off like a lid ; as in 

 the Amaranth (Fig. 298). 



351. A Caryopsis, or Grain, differs from the last only 

 in the seed adhering to the thin pericarp 

 throughout, so that fruit and seed are in- 

 corporated into one body ; as in wheat, In- 

 dian corn, and other kinds of grain. 



352. A Nut is a dry and indehiscent fruit, 

 commonly one-celled and one-seedci, with a hard, crus- 

 taceous, or bony wall, such as tne cocoannt, hazelnut, 

 chestnut, and the acorn (Fig. 21, 299). Here the 

 involucre, in the form of a cup at the base, is called the Cupule. In 

 the Chestnut it forms the bur ; in the Hazel, a leafy husk. 



FIG. 291. Achcniuin nf Mayweed (no pappus). S9S. That of Succory (its pappus a shal- 

 low ciip). 293. Of Sunflower (pappus of two deciduous scales). 294. Of Sneezeweed (Hele- 

 nium), with its pappus of five scales. 295. Of Sow-Thistle, with its pappus of delicate downy 

 hairs. 29P. Of the Dandelion, its pappus raised on a long bealc. 



IG. 297. Utrirle of the common Pipweed (Chenopodium alhum). 



FIC. 298. Utricle (pyxis) of Amaranth, opening all round (circumciBsita). 



FIG. 399. Nut (acorn) of the Oak, with iu cup (or cupule). 



