34 



THE AGRICULTUKAL NEWS. 



jAsrAEY 29, 1916. 



•a proper biological balance between parasites and 

 their natural enemies. Then, again, a moist atmosphere 

 is generally associated with a still one, which condi- 

 tion is most desirable, if not necessary, for the luxur- 

 iant growth of limes anfl cacao. 



Humidity can be artificially induced to some 

 extent by so-called wmd-breaks and overhead 

 shade. Indeed it is probable that the value of 

 such protection chiefly lies in the way of maintaining 

 a humid rather than a quiescent state of the air, though 

 it effects both. 



The degi'ee of atmospheric humidity is determined, 

 -and most people know, by means of a wet and dry 

 Ijulb thermometer. The greater the difference between 

 the two readngs, the drier the air. The relative 

 humidity is calculated on the difference with the use 

 •of a table of factors. This observation of humidity is 

 of as gi'eat, if not of greater, importance than the 

 recording of the rainfall precipitations. Very few 

 -estates, however, take the trouble to carry out 

 the observation systematically, and scarcely any 

 realize its full significance, which is possibly a reason 

 for omitting the practice. Reference to the Annual 

 Heports of the Local Agricultural Departments 

 shows that even officially, observations on humidity 

 are not recorded in some islands, or at least, are not 

 published. Neglect to do so constitutes a very 

 regrettable omission. 



A valuable piece of investigation work would be the 

 -collection of humidity figures from different estates in 

 different islands. It might lead to the solution of prob- 

 lems of growth at present unsolved. The trouble with 

 limes in Montserrat, St. Kitts and Nevis has practically 

 been reduced to a humidity basis. If attention had been 

 given earlier to the idea, a large amount of time and 

 trouble, and probably money would have been .saved. 

 The conduct of humidity observations under wind- 

 break and overhead shade conditions would be 

 productive of especially interesting results, and might 

 settle once and for all, the confiicting statements that 

 one hears concerning the nature of the benefit derived 

 from this form of protection. Closely allied to foliage 

 protection is that of cheese-cloth, under which tobacco 

 grows more vigorously than in the open. This again 

 is to some extent a question of humidity. It is hoped 

 that this jiiid the foregoing considerations will 

 -Stimulate the interest of planters in what is for them 

 a, very vital (|uostion. 



SUGAR. 



STUDIES IN INDIAN SUGAR-CANES. 



Dr. C. A. Barber has issued in the Memoirs of the 

 Department of Agriculture m India, the fiist of a series of 

 papers entitled, Studies in Indian Sugar-cane.s: No. 1, Punjab 

 Canes. This study deals with the canes of a definite area in 

 which it is believed that some of the most primitive sugar- 

 canes in the world occur, and it is thought that the study of 

 these primitive forms may well be calculated to throw light 

 on the origin of the widely cultivated forms whose systematic 

 study presents enormous difficulty. 



Although Dr. Barber laments that this list of morpho- 

 logical characters dealt with in the descriptions is incomplete, 

 it will be found to comprise a far greater number than other 

 ob.servers have yet found it possible to give attention to, and 

 it may well be that the extension of the field of comparison 

 will stimulate other observers in other parts of the world to 

 include a larger number of characters in their critical studies. 



The characters dealt with are: general remarks as to 

 distribution; agricultural, and chemical characters; list of 

 specimens examined; general characters of the variety. 



Cane measurement: Dead leaves at six months old; 

 length of cane and of shoot after stripping these; total 

 length of cane and number of joints at six and ten months; 

 total length divided by average thickness at middle; length 

 of joints in different parts of the cane; thickness of the cane 

 at various points. 



Colour of cane: General; bloom; growth ring; root 

 zone; blackening; blushing; scar line or band; ivory mark- 

 ings, splitting; groove markings. 



Characters of the joint: Thickness, ovalness in section; 

 length of mature joint (deducting top), average longest 

 average shorest (basal); shape viewed medially; shape viewed 

 laterally; leaf scar and its ending, lip; circlet of hairs; 

 groove; root zone; growth ring. 



Bud: Shooting, burst, etc.; size and form; origin and 

 cushion; flanges; bristles, basal patches and minute black 

 hairs. 



Leafy shoot: Colour; terminal tuft of leaves; character 

 of leaf ends; number of terminal joints under 2 inches long. 



Leafsheath: Length; average longest; colouring, bloom, 

 scarious border and edges; hairs on back and on edges; 

 clasping stem; proportional width of sheath and lamina; 

 ligular processes; ligule and hairs on its edge. 



Lamina: Width and length, average extremes, and 

 proportion of these to one anfither; channelling, etc.; 

 transverse marks; serrature; roportional width of midrib to 

 lamina. And eight groups of Punjab canes are then carefully 

 described and figured according to this scheme. 



One of the most striking items provided by an investi- 

 gation of soil gases dealt with in the J/emoirs of t/ie Depart- 

 ment of A(/ricidture in India (Chemical Series, Vol. IV, 

 No. '.i) is the composition of gases in the neighbourhood of 

 the roots of plants. The proportions of carbon didxide 

 found are high; but most striking of all is the low propor- 

 tion of o.xygen, and the presence of hydrogen, which has 

 not hitherto been suspected under these conditions. It is 

 stated that the diffusion of gases through soils at a depth 

 of 12 to 1-5 inches is so efficient as to warrant the cnn- 

 clusion that cultivation of the surface soil is unnecessary for 

 purposes of aeration. 



