The President's Address. By Lord Avebury. 163 



Finally comes the question how the young plant emerges from 

 the seed. A dense thick coat is useful to seeds in protecting the 

 embryo from heat and cold, from drought and enemies ; on the 

 other hand, if the young plant is to grow, it must be able to 

 emerge at the proper time. The outer coverings of the seed 

 must serve as a castle, but not as a prison. Why are seedling 

 larches so abundant in Switzerland or Siberia, and so rare in 

 England ? I throw out the following suggestion : In the high 

 valleys of Switzerland, where the larch is indigenous, there is much 

 snow. All through the winter the seed is soaked in cold snow 

 water, the testa decays, and when the warmth of spring comes the 

 embryo has no difficulty in emerging. In England we have little 

 snow, the seed is comparatively dry throughout the winter, 

 the woody tissue of the testa remains hard and uninjured, and 

 the poor little seedling, unable to escape from its prison, perishes 

 miserably. 



In other cases the testa retains its strength, but splits, so that 

 the cotyledons can easily force it open ; or is provided with a 

 door through which the cotyledons are able to emerge. In such 

 cases they are narrow and elongated. 



In the Water Plantain (Alisma Plantago), where the radicle 

 does not at once elongate, the peculiarly thickened hypocotyl 

 produces numerous hair-roots by which the seedling is fixed in the 

 soil or mud. The single awl-shaped cotyledon frees itself by its 

 own growth. 



In Typha the seed has a sort of trap-door at one end, which is 

 easily pushed open from within by the cotyledon. 



In Trapa the seed is anchored to the mud at the bottom of 

 the water by diverging pointed processes. The cotyledons are 

 very unequal in size : one is quite small and is carried out of the 

 seed ; the other is large and fleshy, serving, in fact, as a reservoir 

 of food. When this has all been absorbed it dies without ever 

 leaving the seed. 



The genus Scabiosa (the Scabious) affords several interesting 

 illustrations of the devices by which seedlings effect their exit. 

 In S. austrcdis the achene closely occupies the interior of the 

 involucel, so that on germination the radicle gets outside imme- 

 diately and pushes down straight into the soil for a considerable 

 depth, at the same time giving off numerous root-hairs (fig. 37). 



If the involucel is fairly well covered with soil, the cotyledons, 

 after the long radicle has established itself, are easily and readily 

 pulled out clear of the seed and its investments. The cotyledons 

 in this species are not very broad, because the seed itself is not 

 very thick. 



The base of the hypocotyl has a thickened projecting ledge, 

 which presses against the rim of the involucel and pins it to the 



