282 FERTILIZATION OF THE OVULES. 



together, are attached separately to the walls of the ovarium 

 as at a. 



435. These two sets of organs are 

 by no means constantly united, how- 

 ever, in the same flower. The stand- 



* ., . 



niferous or stamen-bearing flowers, are 

 frequently distinct from those which are 

 pistilliferous or bear pistils. When they 

 occur on some other part of the same Fl - 84 OVARIUM OK VIOLA 



TRICOLOR ; a, placenta. 



plant, it is said to be monoecious (single- 

 housed); if on a different plant, it is dioecious (or double-housed). 

 Sometimes the same collection of flowers contains some perfect 

 ones, with others staminiferous, and others pistilliferous only. 

 There is reason to believe that, when either set of organs is not 

 developed, the rudiments of it really exist ; for these parts are 

 frequently made to appear by cultivation. 



436. If the ovarium be cut into, previously to the opening of 

 the flower, it will usually be found to contain a great number of 

 the ovules or young seeds. These are at that period quite soft ; 

 and their interior is filled up with a kind of pulp, which is 

 enclosed in two or more envelopes. These seed-coats do not 

 entirely cover the central envelope, but leave a small opening, 

 which is called the foramen. This opening may be easily detected 

 in the perfect seed (although it has there nearly closed up), by 

 soaking it in water, and then pressing out the fluid that has been 

 absorbed, which will be seen to issue from this little orifice. The 

 foramen, as will presently appear, has a very important purpose 

 in the fertilization of the seed; which, at the period now 

 described, contains no trace of the germ of the new plant. 



437. This germ appears to be conveyed into it from the 

 pollen, in the following curious manner. The little grains or 

 cells, when set free from the anthers, fall upon the stigma of the 

 pistil. In general the anthers are situated above the stigma, 

 the stamens being longer than the pistil in flowers that are erect 

 or upright, and shorter in those which hang down ; but some- 

 times a special provision is necessary, for the conveyance of the 

 pollen to the stigma, especially in monoecious or dioecious plants. 



