. Carnegie Institution of Washington publication. Description of the Guayule. 47 composed of three morphological elements, fused above, but more or less loosely connected below; a rare occurrence, analogous to the condition of some stamens. The middle element is the narrowest, and is the bract proper of the pistillate flower. This, to be seen, must be dissected out. Another peculiar feature then be- comes apparent, namely, that the two disk flowers can not be separated from the achene without pulling away two narrow strips of tissue from its margins. (Fron et Francois, 1901.) The whole arrange
. Carnegie Institution of Washington publication. Description of the Guayule. 47 composed of three morphological elements, fused above, but more or less loosely connected below; a rare occurrence, analogous to the condition of some stamens. The middle element is the narrowest, and is the bract proper of the pistillate flower. This, to be seen, must be dissected out. Another peculiar feature then be- comes apparent, namely, that the two disk flowers can not be separated from the achene without pulling away two narrow strips of tissue from its margins. (Fron et Francois, 1901.) The whole arrangement would appeal to the tele- ologist as an excellent adaptation for dissemination by the wind or by water, since the thin, light, and air-imprison- ing tissue may serve as wings or floats according to circumstances. The achene itself is crowned by the persistent but shriveled corolla, and at either side of this and against its ventral (upper or inner) aspect are three short awns,1 one in each position, The achene proper is ovate, with an acute base. It is par- tially clothed with short appressed hairs, but for which the pericarp would be black or dark gray. The achene meas- ures mm. in length by in breadth when of normal size, exclusive of the awns. The "seed" of the two other spe- cies, mariola (P. incanum) and P. hys- terophorus2 (an annual), which grows with or near the guayule, may be distinguished by attention to the char- acter of the lateral awns, which may readily be seen with a lens by viewing them as they project beyond the bract. In the guayule the awns are brown, with papery, denticulate margins. In the mariola these are slender, appearing denticulate or quite without membra- nous margins, tapering and distinctly reflexly curved, and are usually darker in color, being black toward the 1 Taxonomic works usually indicate that there are only 2 awns, but this is an error. There are 3 awns in Parthenium argentatum and P. incanum; 2 in the herbaceous P
Size: 934px × 2676px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorcarnegie, bookcentury1900, bookdecade1910, bookyear1911
