SUPPLEMENT 



hybridization does give rise to new species. A hybrid may be quite 

 as fertile as the parent species, or even more so, and among the many 

 hybrids that arise, some are likely to be better adapted to changing 

 climatic conditions, changes in insect life, etc., than are the parent 

 plants. Kerner claims that the full significance of sex in plants can 

 be explained only in this way ; that is, that the union of the ooplasm 

 and spermatoplasm from different species can give rise to new species 

 better adapted to new conditions. 



To return to the sages and other Labiatae ; the calyxes persist and 

 enclose the four seed-like fruits ; sometimes the calyx teeth attach 

 themselves to passing objects, and so become efficient means of seed 

 distribution, as every one who has encountered the hoarhound knows. 

 But generally the calyxes are not easily broken off ; most persistent 

 calyxes serve as do capsules, simply to hold seeds until they are scat- 

 tered by hard winds. Kerner states that in many cases the teeth are 

 pressed down by passing objects, or against neighboring twigs in a 

 wind, and that in the rebound the fruits are shot out with consider- 

 able force. 



