216 COMPENDIUM OF GENERAL BOTANY. 



been mentioned, but will again be referred to in the discussion of 

 cross- fertilization . 



From the foregoing we may conclude that there are parts of 

 the flower which serve the function of reproduction directly, and 

 parts which aid indirectly. To the first belong the ijynmcium, and 

 the androeciuin, that is, the male and female sexual organs of the 

 flower. The calyx, the corolla, the perianth, the nectaries, and 

 the hypsophyllary leaves aid reproduction indirectly, since these 

 organs may be substituted for one or the other of the inessential 

 organs. The flowers of the pine require no calyx, no corolla, 

 no nectaries, or torus. All such structures would be M'ithout a 

 pur})ose. The flowers of grasses require no calyx, corolla, or 

 nectaries, as their absence indicates. A monocotyledonous flower 

 with a perianth, as the hyacinth, may also be without calyx. 

 Flowers of Pruniis as well as those of many other phanerogamic 

 plants require calyx, corolla, and nectaries for the purj^oses of re- 

 production, as is indicated by their presence. Nature does not pro- 

 duce any useless structures. 



Number, form, and arrangement of floral organs and their parts 

 play a very important role in the morphology of flowers and in the 

 classification of plants. What Linne so fortunately considered to 

 be of importance in establishing his system of phanerogams is 

 emljodied in its essentials in our present system of classification ; 

 that is, the recognition of constant floral characteristics, such as 

 number, cohesion of parts, size, symmetry, etc. The following is 

 a brief summary of such characteristics. 



If the calyx, corolla, stamens, and pistils succeed each other 

 vertically on one axis {receptacle or torus)., we have what is known 

 as a hypogynous flower. The ovary is said to 

 '^''ll^yLf f^/pj ^^ superior (Fig. 136). 



In the second case (Fig. 137) the develop- 

 ment of the floral axis is such tliat the apex 

 Fig. 136.— Hvpoeynoiis appears depressed, that is, a peripheral wall 

 flower (Rammcnla- j-i^es above the apex, so that in the mature 

 (After Berthoid and Lan- structure the ovarv witli its ovulcs lies below 

 the base of the insertion of tlie stamens and 

 petals. Such a flower is said to be epngynous j ovary in- 

 ferior. 



Finally, in the third case (Fig. (138) the stamens and petals 



