212 COMPENDIUM OF GENERAL BOTANY. 



the ripe seeds variously equipped with winged appendages for the 

 purpose of facilitating their distribution by air-currents. EICHLER 

 for a long time considered the seminiferous scale as a " meta- 

 morphosed shoot." The entire cone would therefore be the in- 

 florescence. Now the entire structure is considered to be a single 

 female flower, which bears numerous peculiarly modified seed-leaves- 

 on one axis. STRASBURGER made a special study of conifers. 



We will here note that the stem-structure and the mode of 

 axillary branching represent further differences between conifers 

 and angiosperms. Concerning the differences between the male 

 flowers of gymnosperms and angiosperms we will give further par- 

 ticulars in the discussion of stamens. 



In distinction to gymnosperms the ovule of angiosperms is usually 

 situated at the margin of the carpel ; the latter organ is not flat, 

 but typically arched, forming a hollow structure (the ovary). This 

 organ may be formed from a single carpel or by the adhesion 

 (growing together) of several carpels. These several carpels are so 

 united that the ovules inserted in the margins come to lie in the 

 interior of the cavity so formed. The united margins on which 

 the ovules are inserted are known as placentae. This adhesion of 

 parts, which does not exist in gymnosperms, because it is not 

 required, necessitates still other structural adaptations for the pur- 

 poses of pollination and fertilization. Since the ovary is closed, 

 the pollen cannot be brought to the micropyle by the wind or in- 

 sects. There is a special organ, the stigma (Fig. 132, A), which 

 receives the pollen-grain ; also a second organ, the style (g), which 

 forms the path for the growing pollen-tube (k I m). The seed- 

 leaves (carpels) by their union form a longer or shorter canal at the 

 upper part known as the stylar duct (Griffelkanal). This channel, 

 which is either hollow or composed of soft tissue, is bounded above 

 by the papillose terminations of the carpellary leaves, which con- 

 stitute the stigma. These terminations may differ greatly morpho- 

 logically ; they may appear as fine rays, papillae, etc. The stigma 

 secretes a moist sticky substance to which the pollen-grains adhere 

 and in which they begin to germinate. The pollen-tube extends 

 down the stylar duct into the cavity of the ovary ; special structural 

 adaptations may also exist for conducting the growing pollen-tube 

 to the micropylar opening. In reference to the explanation of Fig. 

 132 the following is added: a, transverse section of anther; r 



