Books and Current Literature. 125 



designate it as a new species under the name of Capsella heegeri. 

 The mode of its occurrence suggested its recent origin from 

 Capsella bursa- pastoris b\- mutation, and in 1901 it was mentioned 

 by De\'ries as an instance of mutation in nature. Solms-Lau- 

 bach investigated the result of self-fertilization and showed 

 that the characters that difTerentiate Capsella heegeri from C. 

 bursa- pastoris are fully heritable. Shull, from whose recent 

 paper on the crossing of Bursa bursa-pasloris and Bursa heegeri 

 (Proc. 7th Intern. 7ool. Congress, 1910) the above is quoted, 

 has tested the question as to what will happen when the two 

 species intercross and presents his results as follows: 



(1) Bursa heegeri has the same Mendelian units in its 

 leaves as occur in B. bur sa- pastoris , which serves further to con- 

 firm its derivation from that form. 



(2) The crossing of B. heegeri with B. bursa-pastoris gives 

 rise to a series of elementary species in the former corresponding 

 with those in the latter species. 



(3) The leaf characters are inherited in strict Mendelian 

 ratios, but the capsule shows a very great departure. 



(4) Under these circumstances the capacity of B. heegeri 

 for self-mahitenance in competition with B. bursa-pjstoris rests 

 upon the comparative infrequency of cross-fertilization. 



"The precipitation is distributed in di.Terent ways in the 

 soil according to its nature and surface, and hence comes the di- 

 vision into formations; it therefore can not be said that one plant 

 for.ration is edaphic and another not, on the other hand they 

 n.ay all be named edaphic, dependent as they are on the humid- 

 ity in the soil; but as the humidity is dependent upon the pre- 

 cipitation, it is n.ost natural to say that they are all climatic." 

 All of which serves to indicate the part that dialectics may be 

 made to play in investigations of this character. 



The studies of West on the British Freshwater Phytoplank- 

 ton, reported in the proceedings of the Royal Society, indicate 

 a dominance of dcsmids in the lakes of Western Scotland, North 

 Wales, and the English Lake District. It is found that the 

 desmid flora increases in richness in passing from the Tertiary on 

 the east to the older Paleozoic rocks of the western part of the 



