K.— BOTANY. 207 



researches on the pollination of the date palm (Phoenix dactylifera L.) 

 which he and Mr. Roy "VV. Nixon* ^ have been conducting. 



' Each species of Phcenix,' he writes in his last letter of May 22, ' seems 

 to have determined its peculiar action in ripening the fruit of the date 

 palm. The most amazing thing is that the pollen of the huge Canary 

 Island palm used on the date palm produces a small, peculiarly pointed 

 seed, quite different from the ordinary date seed, and small or medium- 

 sized fruit that ripens late, whereas the tiny palm commonly called 

 P. Roebelinii, which has the smallest seeds of any wild form of Phoenix 

 known, when used to pollinate the true date palm, causes the formation 

 of large seeds, usually with a curious sunken area about the germ pore 

 and makes large dates which ripen extremely late, nearly two months 

 later than the ordinary crop. Preliminary tests of Phoenix sylvestris, from 

 India, seem to give medium-sized seeds and medium to large-sized dates, 

 ripening earlier.' 



The economic importance and scientific interest of these discoveries 

 need no comment. 



Systematic botanists in the past have, I think, been rather too apt to 

 regard the ' species ' they have described as fairly definite units, recognising 

 and recording from time to time ' varieties,' but, as I have said earlier, 

 frequently without sufficient material to enable them to say what such 

 varieties really represent, or how constant and definite they may be. In 

 some cases they may be the so-called ' Jordanons,' while in others, no 

 doubt, as we are beginning more fully to realise, they are the resultants 

 of hybridisation. For the majority of plants the occurrence of such 

 ' varietal ' forms appears to be of little more than purely scientific interest, 

 and they may be passed by with only a casual comment. 



When, however, almost any plant comes into the limelight of Applied 

 Botany and is found to be of some economic value, then the importance 

 and significance of varietal differences at once becomes apparent. A few 

 cases may be cited in illustration : — 



Para rubber (Hevea hrasiliensis) is considered to be a good botanical 

 species, but a careful examination of the trees now being grown in planta- 

 tions in the East reveals a number of forms, very similar as regards their 

 morphological characters, but showing marked physiological differences, 

 especially with regard to the yield of latex. 



The planter, therefore, who has the good fortune to own a plantation 

 of high-yielding trees is in a favourable position compared with a neighbour 

 whose trees may only yield the minimum quantity of latex. Here again 

 the problem is one for the geneticist to solve, or it may rather prove to 

 come within the province of the horticulturist and involve budding, with 

 the selection of suitable stocks and scions, as is being done in Ceylon, 

 Java and elsewhere, on lines similar to those adopted in relation to com- 

 parable problems with apples, pears and plums at home, which are being 



'5 Swingle, Walter T. ' Metaxenia in the Date Palm,' in Jonrn. of Heredity, 

 Vol. xix, No. 6 (1928), pp. 257-268. Roy W. Nixon, ' The Direct Effect of PoUen on 

 the Fruit of the Date Palm,' in the Journ. Agric. Research, Vol. xxxvi.. No. 2 (1928), 

 pp. 97-128 ; and ' Immediate Influence of Pollen,* in Journ. of Heredity, Vol. xix. 

 No. 6 (1928), pp. 241-255. 



