THE MONTHLY lill.LKTIN. 377 



All the information at hand, then, would indicate that this species is 

 as severe as the citrus mealy bug and should be handled, from a legis- 

 lative standpoint, and treated in much the same way, wiien established 

 in a district. — E. 0. Essig, Department of Entomology, University of 

 California. 



The Agricultural Value of Impermeable Seeds. — The Journal of 

 Agricultural Research, issued August 14, 1916, contains an article by 

 George T. Harrington on "The Agricuiltural Value of Impermeable 

 Seeds." There is so much of interest in this article to the farmer that 

 the writer is giving a short summary of it here, largely in the words of 

 the text, with a few notes and conclusions, in the hope that it will be 

 of assistance to the farmers of this state: 



"By 'impermeable seeds' is meant those seeds all parts of whose 

 seed coats are impermeable to water at temperatures favorable for 

 germination. 



"It is impossible to distinguish between impermeable and permeable 

 seeds except by testing their ability to absorb water at a temperature 

 favorable for germination. 



"The production of impermeable seeds is particularly characteristic 

 of the Leguminosge, but it occurs also in many other plant families. 



* ' Impermeable seeds frequently retain their vitality for many years, 

 sometimes for as many as eighty years. 



"Fresh impermeable seeds germinate promptly when the seed coat 

 is broken or becomes permeable.^ 



"The viability- of fresh impermeable seeds is frequently greater than 

 the viability of fresh seeds of the same species which are permeable. 



"Seeds of the common clovers, alfalfa and hairy vetch, which are 

 impermeable at the end of three or five years under laboratory condi- 

 tions of storage, retain their vitality apparently unimpaired up to that 

 time. The viability of the permeable seeds in the same lots decreases 

 slightly in the second and third year and more in subsequent years. 



"In dry storage nearly all impermeable alsike clover, white clover 

 and sweet clover seeds remain impermeable until at least two or three 

 years old. Impermeable red-clover seeds become permeable gradually 

 in dry storage, but from one-third to two-thirds of them may still be 

 impermeable after four years. The majority of impermeable alfalfa and 

 hairy vetch seeds become permeable before they are two years old. 

 Okra seeds become less permeable as their age increases. 



"Impermeable clover seeds which were thoroughly matured before 

 harvesting soften and germinate more slowly under conditions favor- 

 able for germination than do impermeable seeds of the same species 

 which were less well matured ; they also become permeable more slowly 

 in dry storage. 



"It is impossible to estimate even approximately in advance the 

 proportion of the impermeable seeds in any given lot which will germi- 

 nate in any given length of time under ordinary germination conditions. 



^This end Is sometimes accomplished by scratching the seeds in a macliine before 

 planting. 



^Viability means germinating properties. 



