168 HOFMEISTER, ON 



interior of a mother-cell, is the contraction of the contents 

 of the mother-cell (which contraction usually follows 

 the division into two parts, or the repeated division into 

 two parts of such contents), and the formation round 

 the contracted mass or its divided portions of a new mem- 

 brane, not attached to the inner surface of the membrane 

 of the mother-cell. In plants, where the contents of the 

 mother-cells divide into several portions before the con- 

 traction, the question whether special mother-cells with 

 firm rigid walls are developed or not, depends simply 

 upon the greater or less firmness of the substance which 

 must be secreted by the cell-contents in order that the 

 latter may be able to contract into a smaller space. This 

 substance is always gelatinous, and usually tolerably firm. 

 The thin, fluid nature of the jelly in Gymnosiomum pyriforme 

 forms a gradual transition to the state of circumstances 

 found in Phascum, where the fluid substance which 

 is found between the inner wall of the mother-cell and the 

 contracted portions of the contents, behaves under iodine 

 just like pure water. The latter cases seem to show that 

 the contraction of the cell- contents depends upon an 

 innate vital action, and not upon a mechanical compres- 

 sion (accompanied by the withdrawal of water), caused by 

 the distension of the innermost lamella of the membrane of 

 the mother-cell. 



A great uniformity prevails in the process of develop- 

 ment of the fruit of mosses so far as regards the most 

 prominent features, viz., the cell-multiplication of the 

 young fruit-rudiment, the separation of the sporiferous 

 cellular layer from the remaining tissue of the theca, and 

 the separation of the outer wall of the capsule from the 

 inner one. The deviations from this process exhibited 

 in Arclddium p/iascoides, the ripe fruit of which is itself 

 remarkable, are, therefore, the more surprising. These 

 deviations are reducible to two: 1. Spores are developed 

 by one cell only of the hollow cylindrical layer whose 

 cells in other mosses become, one and all, primary mother- 

 cells : 2. This cell and the daughter- cells produced by 

 the division of its contents, gradually displace the whole 

 of the inner tissue of the capsule. The peculiarities of 



