DEVELOPMENT OF PLANTS 



421 



are rarely perfect, though rudimentary (sterile) stamens may 

 be developed with fertile pistils or vice versa, thus giving the 

 appearance of perfect flowers (Fig. 302, B-D). The calyx does 

 not adhere to the ovary as in the Fagales, though the sepals often 

 cohere (Fig. 302, D). The ovary usually matures as a nut, but 

 in many cases a kind of drupe (page 383) is formed, owing to 



Fig. 303. 



Fig. 302. Inflorescence and fruit of elm, order Urticales: A, twig of elm 

 bearing principally staminate flowers. B, a staminate flower enlarged, show- 

 ing lobed perianth enclosing numerous stamens. C, pistillate flower, two- 

 lobed stigma projecting from perianth. D, section of pistillate flower, show- 

 ing aborted (sterile) stamens and pistil (fertile) of two carpels, as indicated 

 by the two stigmas. E, the fruit with perianth still attached. A wing has 

 grown out from the sides of the ovary. 



Fig. 303. A simple type of the Chenopodiales: A, shoot of Mexican tea 

 (Chenopodium) , showing character of inflorescence, in. B, flower enlarged, 

 showing the perianth, stamens and pistil of three cohering carpels. 



the perianth becoming fleshy and enveloping the nut. The fruit 

 of the mulberry is an aggregation of drupes. In the fig the stem 

 envelops the minute curious flowers and becomes fleshy, forming 

 the edible portion of the fruit. 



141. Orders Showing an Advance over Preceding Forms. — 

 The buckwheat order, Polygonales, containing such familiar 

 weeds as the sorrel, dock (Rumex), and knotweed or smartweed 

 (Polygonum), has perfect regular flowers with a distinct calyx. 



