303 



PLANT STUDIES 



Fig. 323. Cros.s - section of 

 anther of a lily {Biitonms), 

 showing the separating walls 



Tlie opening of the pollen-s;ic to discharge its jiollen- 

 grains (microspores) is called (IcJiiscenre, ^N\n<i\l means "a 

 sjjlitting open," and the methods of 

 dehiscence are various (l^'ig. 3,32). 

 By far the most common method 

 is for the wall of each sac to split 

 lengthwise (Fig. 323), which is 

 called longitudinal dehiscence ; an- 

 other is for each sac to ojjen by a 

 terminal jjore (Fig. 322), in which 

 case it may be prolonged above into 

 a tube. 



241. Megasporophylls. — These 



between the members of each are the SO-Callcd " Carpcls " of Secd- 

 pair of sporangia broken n , ^ . . . 



down at ,, forming a eon- pl^mts, aud ui Angiospcmis they 

 tinu(ais ca%'ity (poiien-sae) are Organized in various ways, but 



which opens by a loncritudi- i j_ ■ i j i 



nai »iit.-.\fter SACHS always so as to inclose the mega- 



sporangia (ovules). h\ the simplest 

 cases each carpel is independent (Fig. 324, A), and is dif- 

 ferentiated into three regions: (1) a hollow bulbous base, 

 which contains the 

 ovules and is the 

 real seed case, 

 k n o w n as the 

 V a r y ; (2) strr- 

 monnting this is a 

 slender more or less 

 elongated process, 

 the sfjile : and (3) 

 usiially at or near 

 the apex of the style 

 a special receptive 

 surface for the pol- 

 len, tlie stifpna. 



In other ctises 

 several carpels to- 



thvvv s 

 \avy ami stylo tii>in.-d 

 (1 pistil (syncm-potisl. 

 Ivies (r/l. ;nul sti^MllUS 

 til (syiK'nriKmsi. shcnvint^ 

 1(1 stigma (//).— Altor 



