R. BRAITHWAITE ON THE HISTOLOGY OF PLANTS. 1G9 



nucleus of the motlier-cell divides into two daughter nuclei, which 

 separate and each again divides in two, so that four free nuclei are 

 seen in each mother-cell, lying in a plane or tetraedrally, and the 

 infolding of the primordial membrane then takes place, lacing in 

 the contents into four portions, and thus forming four daughter- 

 cells. 



The spore mother-cells in the higher Cryptogamia are easily 

 seen by section of young capsules, especially those which have 

 large spores, as the Phascoid mosses, Fegatella conica, &c. 



In Pellia einphylla the wall of the mother-cell bulges out over 

 the four nuclei, and constantly extending in the same direction, 

 w^hile it contracts at the centre, which becomes translucent, the 

 four daughter-cells appear fixed together by pedicels. Division 

 into four in form of rows has only been observed by Schacht in the 

 quadrifid fructification of Corallina and Melohesia. 



Having thus briefly considered the various modes of reproduc- 

 tion in cells, in which, by-the-bye, yon will find no grounds for the 

 statements of some authors that cells may be developed from 

 vacuoles — a process, indeed, which I consider to be impossible — 

 you will at once perceive the value of the microscope in our re- 

 searches, for without it any clear conception of these mysterious 

 processes could never have been attained. Although the subject 

 may appear a dry one to some of you, its importance in the study 

 of the subsequent transformation of cells must be my excuse for 

 devoting so much time to its explanation. 



Illustrative Figures. 

 Plate 7. 



Fig. 1. — Free cell-formation in the embryo sac of Phaseolus multi- 

 jioms. n. nuclei, a. a. young cells, h. more advanced, c. 

 still older, enclosed in the cellulose case. X 670. 



Fig. 2. — Spore formation in Peziza leucoloma. a. spore sac with a 

 central nucleus 72., and several vacuoles r. — b. The same 

 after division of the nucleus into young spores, c. ditto, 

 with the cellulose case fully formed. X 620. 



Fig. 3. — Cell division in Ciadophora glomerata. a. commencing 

 infolding of the primordial utricle, b. the same, more ad- 

 vanced, the line of division marked out ; c. the partition 

 completed, x 400. 



