46 SCIENCE PROGRESS 



characters the different factors are considered in turn, the 

 crossing experiments that have been performed with them and 

 the interpretation of the results observed. 



The same author contributes a study of inheritance in 

 Ricinus communis. Amongst the pairs of characters dealt with 

 were : Red-blush and green stems ; bloom and absence of 

 bloom ; dehiscent and indehiscent pods ; oval and orbicular 

 seeds, in each pair the first-named behaving as a dominant. 

 In respect both to dehiscence and seed-shape the F2 analyses 

 suggest that two pairs of factors are involved since a 9 : 7 ratio 

 was approximated. In the former case the pure dominant 

 probably represents a combination of thin capsule wall with 

 dehiscence. Crosses between large and small seeded types 

 yielded seeds of intermediate size in Fi, and in F2 all grada- 

 tions between the two extremes. The author emphasises the 

 commercial value of the indehiscent strain and of the high 

 productiveness of F4 hybrids. 



In a recent study of height in Pisum, White (Contributions 

 Brooklyn Bot. Garden, No. 20) has shown this to be dependent 

 on the presence or absence of at least five genetic factors. He 

 recognises three types of internode length of which " long " 

 and " very long " are found in tall peas and the short type in 

 dwarfs ; moreover, the internode number may have three 

 ranges in tails, viz. 20-30, 20-40 or 40-60, but in dwarfs 

 ranges from 10-20. 



W. N. Jones, in a suggestive paper on the subject of the 

 nature of Fertilisation and Sex (New Phytologist, Dec. 191 8), 

 compares fertilisation with the attack of a parasite upon 

 its host, infertility being compared with immunity and 

 the fusion product with symbiotic union. The postulated 

 " gynoplasm " and " androplasm " are regarded as more or 

 less segregated at gamete formation. Stress is laid on the 

 necessity for distinguishing between factors determining sporo- 

 phytic sex and those determining gametophytic gender. 



Ecology. — .Harvey and True in a paper of considerable in- 

 terest toecologists (Amer. Journ. Bot. Dec. 191 8) describe experi- 

 ments in which plants of Squash, Soya Bean and Sweet Corn 

 were grown in solutions of different salts with a view to ascer- 

 taining the concentration at which absorption and excretion 

 of electrolytes are in equilibrium. The results obtained seem 

 to indicate an absorption minimum for each species which is 



