104 ANGIOSPERMS AND GYMXOSPERMS [CH. 



naked-seeded Gymnospei^ms while the higher flowering 

 plants are termed covered-seeded Angiosperms. Since 

 the Gyranosperm has no closed ovary, it is also devoid of 

 style or stigma, and the pollen falls direct on to the 

 exposed ovules : in the Angiosperm, on the contrary, 

 there is always a stigma, and generally a style, and the 

 pollen cannot reach the ovule direct, but must fall on the 

 intermediate stigma. 



In the cases we have so far examined the closed 

 carpels are inserted singly and separately on the floral 

 axis and each forms a box-like ovary by itself 



In all cases where the carpels are thus separate the 

 pistil of isolated carpels is termed apocarpous. 



Now let us examine a pistil which consists of two 

 carpels, placed face to face, and which, as development 

 proceeds, grow together at their contiguous margins, so 

 that the right-hand margin of the one fuses with the 

 left-hand margin of the other in each case : such a bicar- 

 pellary ovary is well exemplified by almost any Willow 

 or Poplar (Fig. 22), and as the illustration shows we 

 have again a box -like (here flask-shaped) ovary, but 

 composed of two united carpels, and termed syncarpous. 

 The ovules are as before inserted on placentae belonging 

 to the conjoined margins, but since these margins belong 

 to two different carpels in each case, and there are two 

 placental series on the inner walls of the box, we dis- 

 tinguish them as parietal placentae (Fig. 22, P R). The 

 Willow ovary also has a style and stigma, but the latter 

 is double, indicating one for each carpel (Fig. 22, E H). 



Had Ave chosen the pistil of a Maple we should find 

 two carpels as before, but the conjoined margins so in- 

 turned as to meet in the axis of the ovary, bringing the 

 ovules to the centre and dividing the ovary into two cham- 

 bers (Fig. 42). This kind of placentation is termed aocile. 



