466 Miss L. Digby. [Apri 
sporophyte in this respect. The mean of a considerable number of actual 
sountings in the gametophyte is 43 (fig. 3, a, 6, c). This calculation is 
certainly too low owing to the difficulty of realising every individual when 
dealing with high numbers; 50 is probably nearer the actual figure. 

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Fic. 3.—Diagrams of nuclear divisions. a 6 ¢ in prothallus. a’ 0’ ¢’ in embryo. 
The embryo arises as a direct vegetative outgrowth from the prothallus, 
and, when very young, consists of a rounded mass of cells in which the apical 
cells of the cotyledon, stem and root, are clearly recognisable. The longi- 
tudinal section of an older plant is of a normal type, except for the absence 
of a foot. The nuclear divisions have been carefully worked out, and, as in 
the prothallus, the average number of chromosomes present at each mitosis 
has been taken from several countings. The mean of the numbers obtained 
is 41, but as in the case of the prothallial nuclei, this is certainly too low 
(fig. 3, a’, b’, c’). The absolute number is not, however, of great importance, 
but the close approximation in the results of the chromosome countings of 
the prothallial and sporophytic nuclear divisions, undoubtedly proves that 
there is no reduction during the transition of the sporophyte to the gameto- 
phyte generation. A similar result has been obtained in Athyriwwm Filia- 
femina var. clarissima Jones, where the aposporous growth is formed in 
relation to young but abortive sporangia.* Here, however, the absence of 
reduction is accompanied by cytological features, indicating a transient 
* Bower, loc. cit. 
