GAMETOPHYTE AND SPOROPHYTE. 



229 



of pear fruil, the latter being kept in a moict chamber to prevent drying 

 the surface. 



452. In the spring after flowering the pollen escapes from the anther sacs, 

 and as a result of pollination is brought to rett on the stigma of the pistil. 

 Here it germinates, as ^\'e say, that is it develops a long tube which makes 

 its wa}- down through the 

 style, and in through the ^^L 

 micropyle to the embryo sac, 

 where, in accordance with 

 what takes place in other 

 plants examined, one of the 

 sperm cells unites with the 

 egg, and fertilization of the 

 egg is the result. 



453. Macrospore and embyro sac. 

 three pistils or carpels are united into 

 taria the two carpels are also united 

 carpel. Simple carpels are found in 

 example in the ranunculaceae, the 

 bine, etc. These simple carpels bear a 



-In trillium the 

 one, and in den- 

 into one compound 

 many plants, for 

 buttercups, colum- 

 greater resemblance 

 to a leaf, the mar- 

 gins of which are 

 folded around so 

 that they meet and 

 enclose the ovules 

 or sporangia. 



454. If we cut 

 across the com- 

 poimd pistil of tril- 

 lium we find that 

 the infoldings of the 

 three pistils meet to 

 form three partial 

 partitions which 

 extend nearly to the center, dividing off three spaces. In 

 these spaces are the ovules which are attached to the infolded 

 margins. If we make cross sections of a pistil of the Ma)- 



Fig. 299. J ' \ 



Section of pistil of trillium, fig- 300. 



showing position of ovules Mandrake (Podo- 



(macrosporangia). phylluni peltatum). 



