50 STRUCTURAL BOTANY. [41, 42. 



the receptacle below the ovaries; perigynous, on the 

 calyx around the ovary ; epipetalous, on the corolla, as 

 in Phlox ; epigynous, on the ovary at its summit, and 

 gynandrous (y^, pistil, dv6pe$, stamens) on the pistil, 

 that is, when the stamens are adherent to the style, 

 as in Orchis. Inequality in length is definitely marked 

 in two cases, as tetradynamous (rerpa^ four, dvvaiiu;, 

 power) when the stamens are six, whereof four are 

 longer than the other two, as in all the Crucifers ; 

 didynamous, where the stamens are four, two of them 

 longer than the other two, as in all the Labiates (104, 

 106). 



120. Cohesion is as frequent with stamens as with 

 petals. They are monadelphous (adeA06^ a brother) 

 when they are all united, as in Mallow, into one set 

 or brotherhood by the filaments ; diadelphous in two 

 sets, whether equal or unequal, as in Pea, Squirrel- 

 corn ; polyadelphous, many sets, as in St. Johnswort ; 

 and syngenesious, when they are united by their an- 

 thers, as in the Compositse. Finally, the absence of 

 the stamens altogether, whether by abortion, as in the 



? flowers of Veratrum, or by suppression, as in Oak, 

 occurs in various modes, rendering the plant monoe- 

 cious (5), dioecious ($ $), or polygamous ($ $ ?), as 

 already explained ( 67). 



121. The pollen is in appearance a small, yellow 

 dust, contained in the cells of the anther. When 

 viewed with the microscope, it appears as grains of 

 various forms, usually spheroidal or oval, sometimes 

 triangular or polyhedral, but always of the same form 

 and appearance in the same species. Externally they 

 are curiously, and often elegantly figured with stripes, 

 bands, dots, checks, etc. Each grain of pollen is a 



