PINE- GERMINATION 149 



1. The suspensors, coiled filaments consisting of numerous 

 transparent thin-walled cells. At the ends of the suspensors 

 are borne 



2. The embryos : they are more or less elongated, almost 

 cylindrical bodies : in some cases (only one as a rule in each 

 seed) they may have already formed 



a. An apical cone, which terminates the free, anterior end of 

 the embryo ; this being surrounded by 



b. A whorl of cotyledons of variable number. 



c. The apex of the radicle, directed towards the suspensor 

 (i.e. towards the micropyle of the ovule), and imbedded in the 

 tissue at the posterior end of the embryo. 



Note that there is no definite boundary between the suspensor 

 and the embryo. Also that though polyembryony is the rule 

 that is, a number of embryos are at first formed simultaneously 

 one of these supersedes the rest, and that one alone becomes 

 differentiated as above described. 



Ripe Seed. 



Examine the ripe seed of P. sylvestris, and note the external 

 hard and thick seed-coat : within this the endosperm, which 

 incloses the single embryo. It has numerous cotyledons, 

 and a radicle, the apex of which is directed towards the 

 micropyle. 



Germination. 



Compare plants in different stages of germination, and observe 

 the following points in the process : 



1. The endosperm swells, and bursts the testa. 



2. The radicle protrudes, and curves downwards. 



3. The cotyledons elongate, and push out the stem and their 

 own basal portion from the cavity of the endosperm. 



4. The rest of the seed is usually carried upwards on the apex 

 of the cotyledons, which, with the hypocotyledonary stem, 

 elongate greatly. 



5. The plumule develops, forming numerous acicular leaves. 

 Note that the cotelydons turn green while still protected from 



the light, below the soil, and within the testa. 



