68 



BRACTS. 



The chaff on the receptacle of the composite is another 

 form of the bract, and they are called pa lece. 



The Spatke is a bract which incloses the aggregated florets 

 of a spadix, as in the Arums. 



The bracts which demand the most careful attention of the 

 Btudent, if he expects to encounter with success the large family 

 of plants to which they belong, are those of the grasses. 



Let the student take the Crab-grass, Panicum sanguinalis, 

 as a specimen for examination. It may be found in all places, 

 and in bloom through the summer, and is known by everybody. 

 We find it consisting of three or more spikes of flowers. The 

 flowers of each of these spikes we find arranged on one side of a 

 commou support, called rachis, in two rows. If we take one of 

 these spikes and bend it, we see the flowers, which before lay 

 so closely to the stem, separate from it, and exhibit themselves 

 as little spikelets of about half an inch long. By examina- 

 tion, we find that each of these spikelets is composed of two 

 flowers. Instead of commencing with the outer envelopes, as 

 is common with other flowers, we will commence at the center. 

 We find at the center the ovary, stamens, and pistils ; and im- 

 mediately surrounding the ovary we find two nearly opposite 

 membranous bracts, which we shall call paleo3. Elliott calls 

 them the corolla, and by different authors they have the names 

 of calyx, perianthium, gluma interior, perigoniwn, and gluma. 

 Within the palese of some grasses, as the Bromus, there are 

 two small hypogynous, fleshy, colorless scales, which are called 

 squamula?. Elliott calls them nectaries ; and in other cases, 

 instead of the squamulas, are found bristles, as in the Cyperaceoz, 

 called hypogynous seta. Without the paleaa of our specimen 

 we find two bracts inclosing the others, which are called 

 glumes — the calyx, gluma exterior, and tegmen of authors. 

 The glumes do not always inclose a single flower, but most 

 generally are at the base of the spikelet, and inclose many 

 flowers ; as in some of the Panicums there are two, and in the 

 Bromus several. In some instances there are many glumes 

 with no flowers, as in the Schoenus, the lower ones being 

 empty. It may be adopted by the student as a general rule, 

 that, tlmsc bracts immediately surrounding the stamens and 

 pistils arc paUcB, and all others glumes. 



What is spathe ? What arc paleae in grasses? What are squamulse ? 

 Seta; i W hut aro glumes ? 



