December 28, I'JOT 



HORTI CULTURE 



855 



secured very easily, peaches and apri- 

 cots being probably the easiest of the 

 lot. With these two fruits nothing 

 more is necessary than placing the 

 twigs in water or wet sand in a house 

 where the temperature will run from 

 60 to 80 degrees as a diurnal range. 

 A room used for forcing roses is well 

 adapted for this purpose. Plums and 

 cherries are not quite as easily forced 

 into bloom as peaches, but they would 

 not be called difficult. I have found 

 the best results from forcing these 

 in flats of sand which should be kept 

 damp but not too wet as an excess of 

 moisture is apt to cause a rotting of 

 the part in the sand and a conse- 

 quent withering of the part above. 

 Apples and pears are the most diffi- 

 cult of the fruits to force inside, and 

 yet with a little practise these can 

 readily be brought into bloom with 

 only a small per cent of failures. 

 Good healthy twigs should be selected 

 with from two to five fruit spurs 

 thereon. These twigs should not be 

 longer than fourteen inches, as twigs 

 of greater length are more apt to 

 wither if the temperature runs high, 

 owing to greater evaporating surface. 

 As soon as they are put in the flat 

 they should be wet and then put un- 

 der the bench in a cool room, one 

 that is kept at about flfty for a night 

 temperature being well suited for this 

 purpose. They should be moved into 

 the sun gradually and after about ten 

 days or two weeks they should be 

 moved to a warm room. Ventilation 

 should be given at once if the sun 

 raises the temperature above eighty 

 degrees. Frequently the part of the 

 twig below the sand will start to de- 

 cay. In such a case the twig should 

 be pulled out, the decayed portion cut 

 off and the twig reinserted in a flat 

 of clean sand. By putting in fresh 

 boxes of twigs every few days it is 

 possible to have pollen each day for 

 as long a period as is desired. Pol- 

 len from twigs forced in this manner 

 gives approximately the same results 

 under test in the laboratory as that 

 secured from the field. It will vary 

 considerably from either source so 

 that an exact comparison is impos- 

 sible. 



Laboratory Methods. 

 I have used wholly for hanging 

 drop cultures the glass cells, finding 

 them more convenient to inspect than 

 either the rubber or zylonite. For 

 sticking the cell to the slide and 

 cover slip, the common laboratory 

 mixture of equal parts of beeswa.x and 

 vaseline is very satisfactory and 

 could hardly be improved upon. Great 

 care must be taken that the sealing 

 is tight, otherwise the drop will dry 

 up and the culture be ruined. For 

 fear of some such accident it is bet- 

 ter to make the culture in duplicate. 

 While it is desirable that the labora- 

 tory be kept at as even a temperature 

 as possible, variations of five or ten 

 degrees will not usually be apparent 

 in the growth of the pollen, except 

 that a low degree will retard the 

 growth somewhat. In case the pol- 

 len is being taken from the orchard 

 at the normal blooming season it will 

 be found advisable to take twigs on 

 which the blossoms have not yet 

 bloomed and place them in water in- 

 side until anthers dehisce. This will 

 give not only a moi-e plentiful supply 



of pollen, but also an assurance that 

 no contaminations of the pollen have 

 been caused by insects or wind, bring- 

 ing pollen from other varieties. 



Media. 

 I am not at all sure that the best 

 media for any kind of pollen has been 

 discovered. 1 have used only the 

 standard media, mixtures of sugar, 

 gelatine and water; determining the 

 proper strength for each kind of pollen 

 by trial. Substitution of dextrose 

 for sugar gave no apparent bene- 

 fit and was consequently abandoned. 

 And the use of glycerine either 

 as a substitute for gelatine or 

 in addition to it gave similar negative 

 results. Media of quite different 

 strengths seem to be demanded by dif- 

 ferent fruits. Plum pollen generally 

 gave best results with about fifteen 

 per cent, sugar and one and one-half 

 per cent, gelatine. Cherry with ten per 

 cent, sugar and five per cent, gelatine. 

 Pear and apple twenty per cent, sugar 

 and five per cent, gelatine. Where the 

 per cent, of sugar is too high, 

 the grains of pollen do not ger- 

 minate in such numbers, and the 

 growths are short, although they seem 

 strong and symmetrical. Where the 

 sugar solution is too weak, and parti- 

 cularly where the gelatine is not suffi- 

 ciently strong, the tubes are numerous 

 and long but they are apt to be grainy 

 and irregular in size at different points 

 in their lengths. Bacteria and various 

 ferments tiometimes bother by getting 

 into the media, unless great care is 

 taken to keep everything as sterile as 

 possible by corking the bottles in 

 which the media is kept while it is 

 still hot and by washing slides, cover 

 slips and cells with alcohol or some 

 other quick-drying antiseptic agent. 

 Media should always be neutralized by 

 the use of a few drops of some alka- 

 line mixture as the pollen does not 

 germinate readily in acid media. The 

 media should also be thoroughly 

 shaken in the bottle as soon as pre- 

 pared, a thorough aeration seeming to 

 add to its efficiency. It would sim- 

 plify greatly the question of media 

 preparation if it were possible to 

 analyze chemically some of the stig- 

 matic secretions. The few chemists to 

 whom I have mentioned the matter 

 held but little hope of its being possi- 

 ble. There are two difficulties in the 

 way, first, the probable delicate 

 chemical nature of the compound 

 which might change in a few hours; 

 second, the practical impossibility of 

 securing enough of the fiuid for a 

 proper analysis. At one time when 

 the stigmatic fluid was standing In 

 drops on the pistils of grapes I tried 

 to gather some of it in a watch glass 

 for use in the laboratory, but it would 

 evaporate practically as fast as it was 

 gathered so that at the end of three 

 hours all there was to show was a 

 smeared and sticky watch glass. Even 

 taking it for granted, however, that 

 conditions might be devised under 

 which pollen would make a better 

 growth than under those which our 

 imperfect knowledge of the subject 

 enables us to give, this would not de- 

 monstrate the lack of value of such 

 tests as at present conducted. If all 

 of our standard varieties of any kind 

 of fruit were tested under any kind of 

 conditions that were uniform for all 

 the varieties in question so that the 



comparative strength of all the pollen 

 would be determined, then field tests 

 of any one of these varieties for self- 

 fertilizing power would give a line on 

 all the oihers. For instance, even if it 

 were found that varieties in which less 

 than twenty-five per cent, of the pollen 

 germinated in the laboratory were un- 

 certain bearers when planted by them- 

 selves outside, that would be tangible 

 and definite data capable of being 

 utilized in orchard practice, and this 

 without reference to whether the per- 

 centage of germinations as given in- 

 side were the same as would be given 

 under natural conditions on the stig- 

 matic surfaces or not. 



Pollen Tests. 



In the case of apples, with which I 

 have worked more than with any other 

 fruit, there are a few varieties in which 

 the pollen is nearly all good ranging 

 from ninety to one hundred per cent, 

 germinable. Others give germinable 

 values from this downward, some- 

 times only one or two per cent, of good 

 pollen. I have not found a single 

 variety but that two or three tests 

 would show some germinations. In 

 this respect there is evidently quite a 

 difference between apples and grapes. 

 With the grapes there were a large 

 number of varieties in which all the 

 pollen was good, and an equally large 

 number in which none of the pollen 

 was good, and a smaller number in 

 which the good and bad was mixed. 

 With the apple there are very few 

 with all pollen good, none so far found 

 with all pollen bad, and the great mass 

 showing different proportions of 

 mixed forms. Pollen of the same varie- 

 ty from different trees, and even some 

 time from the same tree, will give 

 varying results. The whole procedure 

 is one of approximations rather than 

 precise determination. There are cer- 

 tain varieties which seem to have a 

 constitutional weakness in the matter 

 of pollen production. Under unfavor- 

 able conditions they furnish pollen 

 with a low germinating capacity. 

 Where the conditions are more favor- 

 able they give a better pollen; but 

 whether favorable conditions for pol- 

 len are the same as favorable condi- 

 tions for tree growth, I have not suf- 

 ficient evidence to say. Three varie- 

 ties in which the pollen appears to be 

 notably weak are the Gravenstein, 

 Tompkins King, and Esopus Spitzen- 

 burg. The Gravenstein being a com- 

 paratively late introduction from 

 Europe is not so well known, but for 

 the last two varieties I believe it is 

 generally recognized that they are 

 raised successfully only in certain 

 neighborhoods — that is under favorable 

 conditions for pollen production. Five 

 varieties in which the pollen was 

 particularly strong are Jonathan, 

 Wagener, Ralls, Wealthy, and Missouri 

 Pippin. All five of these are good and 

 regular bearers. In the case of four 

 of them they have the recognized 

 weakness of overbearing on mature 

 trees, and the fruit being consequently 

 undersize. All are widely distributed, 

 well-known varieties in the sections 

 where they mature. The selection of 

 favorable conditions for the setting of 

 fruit is evidently not necessary where 

 good pollen is borne in the abundance 

 that it is in the case of these varieties. 

 Not enough varieties have been 

 tested, nor in many cases have the 



