38 



PLANT PROPAGATION 



more. Clover and alfalfa "hard seeds" are slow unless 

 treated with sulphuric acid as already indicated (47). 



67. Delayed germination, according to W. Crocker, an English 

 investigator, is due to tlie structure of the seed coats rather than to 

 that of the embryos, as popularly believed. Those coats which ex- 

 clude water are slower than those which exclude oxygen. In nature, 

 growth of delayed seeds results from decay of the seed coats by 

 longer or shorter exposure to germinative conditions. 



In garden practice, advantage is often taken of difference in time 

 of sprouting by sowing quick-germinating and slow-sprouting seeds 

 in the same rows, the former to act as markers of the positions of 

 the rows so cultivation may start at the earliest possible moment. 

 The markers must always be sown very thinly. Radish is a favorite 

 for this purpose, because it sprouts and matures early. 



FIG. 29— CALIFORNIA PRIVET IN OHIO NURSERY 

 This ornamental is one of the leading hedge plants today. 



68. Re-germination of seeds. — Popular opinion is wrong 

 in the belief that seeds once dried after germination are 

 useless for sowing or are necessarily killed. Certainly 

 they are not quite as good, but they may sprout again 

 fully as well as the first time and produce just as good 

 plants. Nowoczek made re-germination tests under tem- 

 peratures varying between 60 and 68 degrees with results 



