For August, 1921 



675 



tury from the famous grass plots at Rothamsted, where 

 the sulpliate of ammcmia i)lots have always been inferior 

 to those treated with nitrate of soda. In dry seasons the 

 difference is most pronounced, and excavations revealed 

 a deeper penetration of the grass and clover roots in the 

 nitrate plots and explained the greater susceptibility to 

 drought of the grasses on the sulphate of ammonia plots. 



"The continued use of ammonium sul|)hate tends to 

 j)roduce an acid condition in the soil."' says Professor 

 Harcourt, O. A. C, Guelph, in speaking of the Rotham- 

 sted exi)eriments. Dr. A. D. Hall, at one time director 

 of that station, wrote as follows : "On the grass plots at 

 Rothamsted. for example, where the manuring has now 

 been repeated year after year for fifty years, very dis- 

 tinct types of herbage have associated themselves with 

 the two manures. Putting aside the prevalence of sorrel 

 as due to the acid conditions, the characteristic grasses 

 on the ]3lots receiving ammonium salts possess a shallow- 

 rooted habit, c. g., sheep's fescue and sweet vernal grass. 



"I well remember in going over the fertilizer plots at 

 Rothamsted, noting that the plots on which ammonium 

 sulphate had been used continuously carried very little 

 grass and, what there was, was very shallow-rooted. Of 

 course ammonium sulphate will tend to increase the 

 growth of grass, and if this becomes luxuriant, as it 

 would, it would choke out the weeds. Anything that will 

 increase the growth of the grass Avill tend to choke out 

 the undesired forms of vegetation. It is quite possible, 

 however, that after a few years of continued use of am- 

 monium sulphate the soil may have become sufficiently 

 acid to destroy growth of legumes and of many kinds of 

 weeds without destroying the quality of the grasses, but 

 it is evident that if continued for a long time even the 

 grasses would be destroyed." — Canadian Florist. 



becomes simply the supporting of the tree ; reinforcing 

 the more active tissues. That this part is not absolutely 

 essential is easily understood upon recollection of hollow 

 trunked trees, which are quite vigorous. — F. C. Bradford 

 in American Fruit Grower. 



PRINCIPLES OF TREE GROWTH 



{Continued from paj^e 673) 

 tendency to do its own digesting of the crude food 

 products and seems to be limited in the extent to which 

 it can draw on other parts for these substances. The 

 intelligent pruner, therefore, perhaps unconsciouslv rec- 

 ognizing this principle, aims lo provide each part with the 

 conditions necessary for its best development. Since sun- 

 light is necessary for its best development, he thins his 

 tree so that every spur has its chance to digest its own 

 food, for experience has taught him that it stands little 

 chance of calling upon other parts at the time food is 

 most needed. Remove the leaves early in the season 

 from a spur and see what a poor apple it develops. Thin- 

 ning out one side of a tree is of no help to the other side 

 unless this thinning happens to admit more light to the 

 unthinned side. 



The isolation of each branch may be utilized by the 

 skillful pruner in many ways. To cite one ca.se: he may 

 be confronted by a forked branch, both limbs being of 

 equal size. This forecasts, sooner or later, a bad crotch. 

 If he cuts thom back uniformly the response is uniform 

 and the condition is not imjiroved. Let him cut one more 

 heavily than the other. In the Spring both draw upon 

 the accumulated reserves of the tree and push into 

 growth. The longer limb, however, having a larger leaf 

 area, has a stronger "pulling power" for ascending sap 

 and the same larger leaf area gives it local superiority 

 in elaliorated foods. The result is that it outstrijis the 

 limb that was cut back more heavily, and will in time 

 relegate it to the position of a minor side branch. 



.\s the trunk enlarges the wood at the ceiiter loses 

 its vital functions and retires from active participation in 

 the tree's life. This area roughly conijjrises what is 

 comnionlv known as heart wood and its chief function 



THE GREENHOUSE MONTH TO MONTH 



{Continued from page 671 ) 



have completed their growth, and the sheath is apparent. 

 Less water now. Dendrobium plialcrnopsis has perfected 

 its bulb, and the spike is at the apex. Protect them from 

 snails with cotton batting. One who is careful in water- 

 ing takes into consideration the state of the weather ; the 

 orchid's growth, whether growing or resting; the kind 

 of house it lives in ; and every little item. If you are not 

 careful with watering, you are not a successful grower. 



Hang Cattleya ,:^'igas against the open ventilators, 

 where they can take their rest and break in fuller vigor 

 than e\'er. 



PROPAGATING FERNS 



'T'HERE are several ways of propagating ferns, some be- 

 ■*• mg more suitable to certain genera than others. This 

 article wnll be confined to a description of one method, 

 which is probably the commonest, and certainly the most 

 interesting. 



Spores (so called from the word ".spora,"' a seed) 

 closely resemble seeds. Whereas, the former, however. 

 include in their structure both an embryo (or young 

 plant), protoplasm and an outer covering, the latter is 

 actually the young plant in a very minute form. Seeds 

 also produce flowering plants — spores otherwise. 



The formation of the spores is as interesting as it is 

 complex they are generally found on the undersides of 

 the fronds or leaves, as they are commonly though incor- 

 rectlv termed. The time to gather them is as .soon as 

 thev turn brown, but before they become over-ripe and 

 burst. Including the frond, they are put in a paper bag 

 for a few days to dry, but should be sown as soon after 

 this as possible to get good results. 



Shallow pans are the best receptacles in which to sow 

 them. Half fill with clean crocks and cover with a rnix- 

 ture of peat and leaf-mould, with the addition of a little 

 sharp sand. or. better still, broken bricks, to keep it open 

 and sweet. This should be sterilized by immersing in 

 boiling water or baking in an oven. 



In sowing the spores, take care there is no draught, 

 otherwise being so small and light, they are liable to get 

 lost. Cover the pans with a sheet of glass which should 

 not be removed till after germination, as foreign spores 

 are liable to be blown in and crowd the others out. 



The first thing to be seen when germination has begun 

 is a growth called the "prothallus," which looks like com- 

 mon moss, r.efore the first true frond ajipears, the.se 

 should be pricked out into boxes or pans prepared in 

 the same way as .seed boxes, but slightly rougher in tex- 

 ture. Great care must be taken in the handling of the 

 prothallus. as it is extremely tender, and is liable to die 

 if subjected to the least bruise. The death of one afTects 

 others. 



Soon after this, they should be potted up into small 

 l>ots, using a compost of leaf-mould, peat. plent\- ol 

 shari) sand, and a little loam. 



All should be left in a warm house till they are taking 

 root in the pots, when they may be hardened off (if a 

 hardv species). 



Spring and summer arc the best times of the year for 

 the operation, but it may be done successfully at any 

 season. — Canadian Florist. 



