90 BOTANICAL GAZETTE [January 



Although in substantial agreement with the conclusions of Farmer and 

 Moore, 2 this interpretation of maturation is directly opposed to that of 

 Gregoire 3 and Yamanouchi, 4 who hold that the double heterotypic spirem in 

 Osmunda arises from a conjugation of thin threads, each representing an entire 

 chromosome, as stated in the first paragraph of this review. The Gregoire 

 school charges the Farmer school with a misinterpretation of the presynap- 

 tic stages, while the latter charges the former with a neglect of the second 

 contraction stages. It is not to be denied that the view stated fully by Miss 

 Digby has certain advantages: it allows one interpretation to be placed 

 upon the double spirem in both somatic and heterotypic prophases, irrespective 

 of the exact time at which the split originates, and it also helps to explain the 

 sudden appearance of the split for the second maturation mitosis in the 

 anaphase of the first. 



This question, however, must be settled primarily by direct evidence. It 

 is obvious that its solution depends upon the exact manner in which the 

 telophasic transformation of the chromosomes and the derivation of the latter 

 from the reticulum in prophase are accomplished. It is granted by both sides 

 that the alveolar or reticulate condition in which the chromosomes are found 

 in late telophase is continuous w r ith the similar condition seen in the succeeding 



■ 



prophase. If, therefore, it is true (i) that the telophasic transformation 

 (alveolization) represents a true splitting, and (2) that the early prophasic 

 reticulate condition passes directly into the double spirem, it follows that this 

 doubleness in every prophase is due to the fission which originated in the 

 preceding telophase, as held by Miss Digby. Contrary to the statement of 

 that author, however, workers on mitosis are not at all generally agreed that 

 the evolution of the chromosomes is that stated in (1) and (2). In his investi- 

 gation of somatic mitosis in Vicia Faba for the purpose of elucidating these 

 points, the reviewer, 5 contrary to the findings of Fraser and Snell, 6 Fraser, 7 

 and others, showed not only that the telophasic alveolization is too irregular 

 to permit of its being regarded as a splitting, but also that the reticulate 

 condition of the prophase, instead of developing directly into the definitive 

 split, gives rise to simple thin threads in which a new split develops. From 



2 Farmer, J. B., and Moore, J. E. S., On the meiotic phases in animals and 

 plants. Quart. Jour. Micr. Sci. 48:489-557. pis. 34-41. 1905. 



3 Gregoire, V., La formation des gemini het£rotypiques dans les vegetaux. 

 La Cellule 24:369-420. ph. 2. 1907. 



« Yamanouchi, S., Chromosomes in Osmunda. Bot. Gaz. 49:1-12. pi. 1. 1910. 



« Sharp, L. W., Somatic chromosomes in Vicia. La Cellule 29:297-331. pis. 2. 



1913- 



6 Fraser, H. C. I., and Snell, J., The vegetative divisions in Vicia Faba. Ann. 

 Botany 25:845-855. pis. 62, 63. 191 1. 



7 Fraser, H. C. I., The behavior of the chromatin in the meiotic divisions of 

 Vicia Faba. Ann. Botany 28:633-642. pis. 43, 44. 1914. 



