HOW PLANTS LIVE AND WORK. 329 



growth, and each pushes out a long tube which grows down 

 between the cells of the style, the " neck " of the bottle-like pistil. 



The living protoplasm of the grains grows out into the pollen 

 tubes, and keeps near the tips of the tubes as these continue their 

 journey down the style. At length the tubes enter the ovary and 

 find the ovules. Each ovule has at one end a minute pore, and 

 marvellously enough the pollen tubes " make " straight for the 

 pores and enter them. How they find their way with such 

 unerring accuracy we do not at present know. The protoplasm 

 of the pollen tube fuses with that of the ovule in the neighbour- 

 hood of the pore, and fertilisation is effected. 



The whole process is beautiful in the extreme, but its ultimate 

 rationale is still one of Nature's secrets. This, however, seems to 

 be clear ; a cell in itself sooner or later attains a state of senility, 

 notwithstanding the mysterious power of its living protoplasm to 

 make fresh living matter from dead food. This state of senile 

 decay can, however, be indefinitely postponed by fusion with 

 living protoplasm from another individual. Hence, while an 

 ovule of itself is doomed to ultimate death, the union of its pro- 

 toplasm with that of a pollen grain stimulates it to renewed 

 activity, and actually gives it the power of dividing and subdivid- 

 ing until it forms a new plant with all the powers of its parent. 



Reproduction is an expensive process for the plant, yet 

 without this process all plants would very shortly be extinct. 

 Hence each must periodically put aside the question of its own 

 individual welfare, and devote itself to serious work for others. 



And it is precisely those races of plants which make the 

 largest sacrifices to secure the well-being of their offspring, which 

 attain to the highest positions in the world. We shall see that the 

 lowest plants have the most primitive methods of multiplication, 

 and in most cases make only the very smallest provision for their 

 young. 



While the process of fertilisation described above for the Wall- 

 flower is in all essential particulars similar to that adopted by 

 other flowering plants, the mechanism for securing cross-fertilisa 

 tion used by various other wild flowers is very complex, and often 

 startlingly ingenious. 



