22 



PLANT I'KOPAGATION 



pjufierjieat. The seed of each species, and even some 

 varieties of a single species of plant, seem to demand 

 different degrees or quantities of one or more of these 

 factors to produce best results. The most favorable 

 combination of these factors for each kind of seed is. 

 therefore, called the optimum for that species. Age and 

 stage of maturity of the seeds exercise more or less 

 influence upon germination. Presupposing viability, 

 which means ability to live, the steps or stages of ger- 

 mination are : 1. Absorption of 

 moisture by the seed. 2. Conver- 

 sion of stored food under favor- 

 able temperature into sugars by 

 enzymes or natural ferments. 3. 

 Stimulation of the embryo cells 

 into growth. 4. Bursting the 

 seed coat by the swelled embryo, 

 etc. 



36. Water is necessary in ger- 

 mination because plant food must 

 be in solution to be of service to 

 the embryo. It is, perhaps, more 

 important than oxygen and heat 

 because too much or too little may prevent germination. 

 Therefore, in practice, it requires careful regulation. 

 Generally it reaches the seed through the soil, though 

 many seeds and spores sprout on any surface moist 

 enough, or any material which will supply their needs. 

 In nature there are many variations. Cocoanuts will sprout 

 among rocks where thrown up by the sea, their roots sustained by 

 the "milk" while searching perhaps several yards for crevices in 

 which to secure a hold and food. Countless kinds of seeds blown by 

 wind or carried by water sprout among mountain rocks where both 

 soil and water .are in very small supply. Spanish moss seeds ger- 

 minate on the limbs of trees. Mistletoe does this also, but the 

 sprouts take parasitic root in the tissues of the tree to which they 

 attach themselves. 



Still water retards germination. In the case of buckwheat grown 

 experimentally, most seeds sprouted in 24 hours in running water, 

 but those in still water took two days or more. 



FIG. 16— CUTTING FRAME 

 FOR WINDOW 

 A bandy device for school- 

 rooms. 



