Vegetable Physiology. 365 



thers, or receptacles of pollen, which evidently correspond 

 with the capsules or spore-cases of the Cryptogamia, burst 

 when their contents are mature, and scatter the grains. They 

 have various ways of opening ; sometimes they split along 

 their length, as in the Lily ; sometimes transversely, as in the 

 Duckweed ; sometimes by little pores at their extremity, as in 

 the Potato ; and sometimes by valves, as in the Barberry. 

 These different methods of opening are characteristic of differ- 

 ent tribes of plants. 



The ovarium, or seed vessel, is the part in which are formed 

 the young seeds or ovules, and occupies the centre of the flower. 

 Sometimes this part consists of several evident divisions, and 

 in other cases these are united together more or less closely. 

 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. They are at this period quite soft ; and their inte- 

 rior is filled up with a kind of pulp, which is enclosed in two 

 or more envelopes. These envelopes or seed-coats do not en- 

 tireiv cover the central part of the ovule, but leave a small 

 opening, which is called the foramen. This opening may be 

 easilv detected in the perfect seed, (although it has then 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 has a very important purpose 

 ia the fertilization of the seed, which, at the period now des- 

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



This germ appears to be conveyed into it from the pollen in 

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

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

 the pistil. In general the anthers are situated above the stig- 

 ma ; the stamens being longer than the pistil in erect or upright 

 flowers, and shorter in those which hang down ; but sometimes 

 a special provision is necessary for the conveyance of the pol- 

 len to the stigma, especially in monoecious and dioecious plants. 

 This operation is often accomplished by insects, which ingoing 

 from flower to flower in search of honey, cover their bodies 

 with pollen-dust, and rub it against the pistils of other flowers. 

 When the pollen falls on the stigma, it is retained by a glu- 



