Vol. IX. No. 214. 



THE AGRICULTURAL NEWS. 



22:3 



for canker in the other West Indian Islands, it is at any rate 

 evident that every possible means for tlie siqipfession ofblack 

 rot should be undertaken, and that where the nature of the 

 ground permits, spraying with Bordeaux mixture on a large 

 scale may even be found remunerative. Another preventive 

 measure is to plant only those varieties of cacao which are 

 reasonably resistent to the disease. These preventive measures, 

 taken in connexion with the remedial measures already in 

 practice, should prove capable of reducing the prevalence of 

 the disea.se to a minimum Even if canker disease is not 

 always due to Phylophthora omnii'ora, but is 'in reality attri- 

 butable to Spimria coloratis, or some sjiecies of Nectrin in 

 certain instances, yet the practicability of spraying with 

 Bordeaux mixture is worthy of consideration, as it would 

 certainly tend to reduce canker, in addition ^6 attaining its 

 main object, namely, the reduction of pod diseases. 



GERMINATION AND FERTILITY OP 



POLLEN. 



The fourth of the Research Bulletins iliat are 

 being issued by the University of Wisconsin has the 

 title »SV»ie Condltionn ivhich injio.imce the .Germina- 

 tion and Fertility of Pollen . The following information 

 is taken from the conclusions that were reached, on the 

 completion of the work described in the bulletin: — 



(1) The germination and subsequent growth of tlie 

 pollen tube are very similar to the germination of ordinary 

 spores, and the growth of the hyphal thread. The changes 

 taking place in the pollen grain previous to the germination 

 are undoubtedly similar to those that tike place in the germ- 

 ination of the seed, and the necessary conditions for germina- 

 tion of the pollen grain are the same, that is, heat, moisture, 

 oxygen and a suitable medium. 



(2) The first noticeable change is the swelling of the 

 grain, due to the imbibition of water, an'd the rate of 

 imbibition dei)ends on the temperature, concentration of the 

 culture media, and in some cases upon sunshine. The greater 

 the concentration, the less rapid is the imbibition and germ- 

 ination. In these experiments, the presence of diastase and 

 invertase has been confirmed both in the pollen grains and in 

 the tissues of the style and stigma. 



(3) Most pollen grains will germinate in a solution of 

 cane sugar. The degree of concentration differs with the 

 different species of plants. It is possible that the degree of 

 concentration of the medium in which the pollen of different 

 species are capable of germinating and growing may, to 

 some extent, be a barrier against promiscuous cross-fertil- 

 ization in nature and horticultural practice. However, 

 in most cases, the range is .sufficiently great to overcome these 

 obstacles, if there were not other difficulties in the way. 



(4) No definite statement can be made 'as to the exact 

 manner of growth of the pollen tube. The movement of 

 reserve food from the pollen grain down to the tube was 

 clearly noticeable, but it cannot be stated whether the fecund- 

 ating nucleus, which appears at the end of the pollen tube 

 when it has reached its maximum growth, migrated from the 

 pollen grain or was in the pollen tube. The limitation to the 

 growth in length of a given species of pollen may be, and 

 undoubtedly is, a barrier against cross-pollination of relative 

 species and varieties. 



(5) The vitality of pollen is not seriously affected by 

 temperatures raging from 25° to 5.5°C. in a dry atmosphere. 

 Temperatures under 2-5" seriously interfere with the germina- 



tion. A temperature from 70° to 80° C, in a .saturated 

 atmosphere, is fatal to the pollen of the peach, apple and 

 plum. At a temperature' of 40° to .50°C., in a saturated 

 atmosphere, the grains burst open on account of the rapid 

 imbibition of water, and the number of burst grains increased 

 with tlie temperature. 



(6) Sun.shine had little or no effect on the germination 

 of pollen, or upon the growth of the pollen tube, in most 

 plants. _ There was, however, a slight increase in the rate of 

 growth in favour of sunshine. The germination and growth 

 of the pollen of the tomato are decidedly retarded by cloudy 

 weather, and also the anthers of the tomato require a certain 

 amount of sunshine for the proper development of the 

 jiolien. The same is true in several species of Liliuni. 



(7) The lack of cultivation and fertility in orchards 

 greatly injures the production and fertility of pollen. 



(8) Pollen may safely be shipped from one part of the 

 country to another without losing viability or fertility. 



(9) Experiments indicate that the length of time 

 required for the germination is considerably less than is 

 commonly believed. Two or three bright, warm days, at 

 the time of full bloom, are sufficient for the setting of the 

 fruit. The stigmas of the apple are receptive from four to 

 six days, whether pollinated or not. Continuous rainy 

 weather for six days would probably result in total failure of 

 the crop. 



(10) The factors which affect the fertility and production 

 of pollen, over which the orchardist has control, may be briefly 

 stated as follows: suitable site, location and soil: pro|)er plant- 

 ing, cultivation, and sufficient amount of plant food: pruning 

 and S[)raying; selection of suitable varieties propagated from 

 bearing trees: and the planting of several varieties which 

 flower at about the same time, to insure proper fertilization. 



(11) The factors over which the orchardist has little or no 

 control are: freezing temperature, which may kill the pistil 

 or the pollen, especially before the latter is ripe, or both; 

 continuous rain during full bloom of the orchard; high 

 temperature with a large amount of moisture, and absence of 

 wind, which causes much pollen to burst at the time of ger- 

 mination; and ab.sence of insects and wind at the time of full 

 bloom. 



The Care of Pastures. — Attention has been given 

 recently to the condition of pastures, in Eastern New York 

 and the New England States, by the Bureau of Plant Indus- 

 try of the United States Department of Agriculture, and the 

 results of the work that has been done are presented in Circu- 

 lar No. 49 of that bureau. Some of these are of more gene- 

 ral interest, and may be given as follows: (1) In the corn belt, 

 the practice is to build up badly worn land by using it as 

 a pasture for cattle, whereas the treatment that has been 

 received by pastures in Eastern New York and the New 

 England States has caused thtm to deteriorate greatly: (2) 

 grazing too early, and too close grazing, are harmful, the latter, 

 because the plants are left without sufficient leaf surface for 

 nutrition and because it allows dangerous weeds to become 

 established: (3) remedial measures for worn out pasture.'! 

 consist in: the prevention of over-grazing, the prevention of 

 too early grazing, manuring, cultivating, re-sowing and the 

 eradication of weeds. 



