226 



THE EVOLUTION OF SEX. 



of the axis is furthest from the source of nutritive supply ; with 

 exaggeration, we might call it the starvation-point. There, 

 with katabohc conditions tending relatively to predominate, the 

 reproductive organs are situated. The flower occupies a kata- 

 bolic position, and is often the plant's d3Tng effort. 



In the tiger-lily, growth at first tends to remain continuous, 

 and the base of the bulb bears simple vegetative buds. Further 



rr. 



^^1^ 



The ^Moonwort Fern (Botryc/izum 

 luTiare)^ showing the con- 

 trasted frond {a), and fructi- 

 fication ((5). — After Sachs. 



Diagram of the Tiger Lily, show- 

 ing bulbils {a) in lower axils, 

 and flower above. 



up, however, where nutrition reaches its maximum, the axils of 

 the leaves contain buds, which are separable though still 

 asexual. Finally, further up still, where nutrition is relatively 

 less active and katabolism is maximised, the formation of 

 flowers indicates the appearance of sexual reproduction. 



In manv ferns, the contrast between the ve2:etative and re- 



