1903] MITOSIS IN PELLIA 45 
that he would be rash, indeed, who would claim that all such 
accounts have no foundation except in perverted imagination and 
preconceived theories. That theories suggested by the accounts 
of zoologists and supported principally by misinterpretations of 
plant structures have caused exaggeration in the drawings and 
descriptions of botanists is probably true. While we believe that 
most of these centrosomes are to be interpreted as chance gran- 
ules, nucleoli, pieces of chromosomes, etc., still we see no reason 
why a centrosome or centrosphere might not occur occasionally 
through atavism. The finely granular areas which have been 
noted during spermatogenesis in Coniferales, and the similar 
areas which are often seen in angiosperms, are, in our opinion, 
vestiges representing historically the centrosphere as it appears 
during the early mitoses in the germinating spore of Pellia. 
The blepharoplasts described for various pteridophytes and 
Symnosperms are, in our opinion, to be interpreted as centro- 
somes. It seems to be true that in Ginkgo (17), Cycas (19) and 
Zamia (39) they appear only in the body cell and in the 
Spermatozoids. In Marsilea, however, Shaw (2g) traced them 
another cell-generation farther back, and in the same genus 
Belajeff (2) found blepharoplasts even during the earlier stages 
in the development of spermatogenous tissue. But granting 
that the blepharoplast appears during only one or two cell-genera- 
tions, this does not seem to be a valid argument against its 
centrosome character, for in Pellia the centrosphere is clearly 
distinguishable during only a few mitoses, and even in the mul- 
ticellular thallophytes, if the centrosome should prove to be 
present throughout the life-history, it is at least much more 
Conspicuous at some phases than at others. Plants furnish 
numerous illustrations of the gradual reduction, and even the 
disappearance, of organs during phylogeny. Most botanists 
admit that in the earliest sporophytes all the cells were sporoge- 
nous; but, during phylogeny, portions of the sporogenous tissue 
became sterilized until the sporogenous tissue finally became 
much limited in extent and now appears only during a few cell- 
generations. During such reductions, functions of cells or 
organs may become completely changed, as in the case of the 
