INCOMPLETE FLOWERS. 



33 



appearance seen in the thistle, — a purple or yellow and rayless mound. 

 When both kinds are present, the central florets are called " florets of 

 the disc," and the marginal ones " florets of the ray." 



<^f^ 



Fig. 65. 



Tubular floret 



(magnitied). 



Fig. C6. 

 Conij)oun(l Flower. 



Fig. 07. 



Ligulate floret 

 (magnified). 



It is by no means unusual to find simple flowers densely packed 

 together into cushion-like heads, somewhat resembling the cornucopias 

 of the truly compound, as in thrift, the scabious, and even in clover. 

 The former are even siuTOunded by a basket, but their anthers are 

 distinct, and stand widely apart ; while in the clover the corolla is 

 irregular, and the basket not developed. 



I?icomplele Floivers. 



While complete floAvers, both simple and compound, are provided 

 with a perianth, either single or double, and are usually conspicuous 

 and ornamental, " incomplete" flowers ai-e destitute of this part, and 

 often have their stamens and pistils entirely unprotected, as happens 

 in the ash-tree. The arum would be in the same condition were it not 

 for a peculiar organ called a " spathe," that serves as a hood or cowl. 

 The flowers of unisexual plants, especially unisexual trees, are almost 

 always incomplete, the stamens being covered only by a little scale 

 or "bract." This is the case with fir-trees, the oak, the wil- 

 low, the poplar, and the water star-weed. Grasses, instead of calyx 

 and corolla, have the membraneous coverings exemplified in the chaff 

 of wheat, which is no other than the withered and dried envelope of 

 the stamens and pistil. A great distinction exists, however, between 

 the flowers of grasses and a]l others that are incomplete, namely, in 



4 



