April 1908.] 



357 



Miscellaneous. 



The procedure followed in testing the 

 purity of a seed is quite simple. A defi- 

 nite weight, varying according to the 

 kind of seed, is taken from an average 

 sample of the bulk. The impurities of 

 the two kinds already mentioned are 

 separated out, weighed, and expressed 

 as a percentage. A difficulty arises in 

 some cases where the seeds are blind or 

 deaf, i.e., have all the external characters 

 of the true seed, but lack the kernel. 

 This is especially the case in such a grass 

 as the meadow foxtail. In some cases 

 this seed is pure chaff. When the seed 

 is examined by transmitted light the 

 presence or absence of the kernel is 

 observable. In the great majority of 

 Stations these blind seeds are treated 

 as impurities, bub where seed is bought 

 by the bushel (or by volume) it would be 

 more equitable to include them in the 

 germination test. 



3. Germination. 

 The seed from which the impurities 

 have been removed is taken, aud from it 

 a definite number, varying: according to 

 the seed under inquiry— 200 to fOO gener- 

 ally — is separated without selection, 

 and placed under suitable conditions of 

 temperature, air, and moisture for ger- 

 mination. At the end of a certain time, 

 from a few days in the case of clovers 

 and flax, to 28 or even 33 days in the case 

 of some of the Poas, all the seeds capable 

 of germinating will have sprouted, and 

 can have been counted. I a this way the 

 percentage of germination is obtained. 

 This varies from seed to seed, but should 

 not vary much for the same kind, even 

 from season to season, when the seed is 

 ripe and fresh. Excellent work was 

 done by Mr. W. Carruthers, f.r.s., the 

 Consulting Botanist to the Royal Agri- 

 cultural Society, when that Society was 

 led to issue a schedule of agricultural 

 seeds indicating the minimum percent- 

 age of germination of each kind which 

 the seedsman should be asked to guaran- 

 tee to the member when purchasing 



The riper and more perfect the seed, 

 the more quickly and uniformly will it 

 germinate. This is called the Germinat- 

 ing Energy, and is usually expressed in 

 an Interim Report. Old and not well 

 " filled " seeds have a low and irregular 

 germinating energy. Some seedsmen 

 seem to act on the view that a seed is 

 never too old to be sold, and save seed 

 from one year to another year on the 

 ground that next season, owiug to 

 adverse weather, there may be a short- 

 age of supply. Such prevision aud pro- 

 vision are supported by the statement 

 that, in some cases, two-year old seeds 

 give better plants. In the majority of 

 cases, one-year old seed is the best to 



sow. Prom two years on, seeds lose 

 their vitality by degrees. 



4. True Value. 



It is obvious that one gets an imper- 

 fect idea of the quality of a seed by 

 considering the purity aud germination 

 apart from one another. A seed may be 

 pure, but of low germinating power 

 through age, "heating," want of ripe- 

 ness, etc. Another seed may be very 

 impure, but what there is of it, true to 

 name, may germinate well. Either 

 report, alone would be misleading. I had 

 one sample of Timothy grass to test, 

 intended for experimental work. It was 

 pure and looked good seed, but germi- 

 nated only 10 per cent. It was in conse- 

 quence useless. Hence it is usual to com- 

 bine the purity and germination per- 

 centage to get the True Value of tbe seed 

 This is expressed by the following for- 

 mula, where 



P= percentage of purity. 



G = percentage of germination, and 



TV=True Value. PxG 



= T V. 



100 



Thus a sample of perennial rye showing 

 90 per cent, purity and 80 per cent, ger- 

 mination has a true value of 72— i.e. every 

 100 lb. contains only 72 lb. really good 

 seed. 



In the Irish Station the percentages of 

 purity and germination are stated 

 separately. 



Many factors affect the germination 

 of a given seed. We are not yet in a 

 position to say what is the best or opti- 

 mum condition in each respect for the 

 production of the highest degree of 

 germination in the laboratory of each 

 particular kind of seed. In nature the 

 seed is still less placed under the opti- 

 mum conditions in every respect • it is 

 in consequence usual to assume that the 

 percentage of germination in nature will 

 be 5 per cent, less than under the more 

 or less controllable artificial conditions 

 further, 5 to 8 percent, is allowed as a 

 margin of error in cases of dispute in 

 estimating percentage of germination in 

 the Seed Station. (Advantage is some- 

 times taken of this by the trade to add 

 on to a Stations report 5 to 8 per cent.) 

 ine poorer and more uneven the seed 

 the greater will be the difference in two 

 tests of it even under apparently iden- 

 tical conditions. One is apt to lose sight 

 ot the fact that the object of testing the 

 seed should be, not to obtain the highest 

 possible degree of germiuation under the 

 most perfect artificial conditions, but tc 

 secure a good working idea of the 

 germinating power of the seed when 



