THE HIGHER CRYPTOGAMIA. 291 



character throughout. The three outer membranes when 

 young are far more capable of distension than at a later 

 period, and during this condition the second and third 

 membranes are not without a high degree of elasticity, 

 which diminishes as the capacity of distension becomes less, 

 or even disappears altogether. 



Sanio* has made some interesting observations upon the 

 abnormal formation of elaters out of the membranes of 

 mother-cells in which the division into four daughter- 

 cells has been suppressed. Since these observations it can 

 hardly be doubted that the outermost membrane, which is 

 transformed into elaters, must be looked upon as their 

 special-mother-cell. The Equisetacese, therefore, exhibit 

 the rare circumstance of the persistence of the membrane 

 of the special-mother-cell, a fact which, as far as I know, 

 occurs in phsenogains only in Maranta Zebrina. During the 

 transformation of the membrane of the special-mother-cell 

 into elaters a change in the substance of the membrane 

 appears to take place. Spiral strips of the membrane be- 

 come thinner and ultimately disappear, whilst other strips 

 parallel to these increase in thickness. The differentiation 

 of the membrane in a superficial direction into strips of 

 different characters, may be compared with its differentiation 

 in the direction of the thickness into two lavers of different 

 properties. 



In the ripe spores the central globular nucleus is very 

 clearly visible floating in the yellowish oleaginous fluid 

 contents, in which, even before the shedding of the spores, 

 numerous chlorophyll granules are seen. The number of 

 the latter increases rapidly when the spores are sown on 

 moist ground. After a few hours the primary nucleus 

 vanishes. In its place two new ones make their appearance, 

 the position of which can often only be made out by means 

 of the agglomeration of chlorophyll-granules in their 

 neighbourhood (PL XXXVIII, fig. 12). Between the two 

 a septum is formed, dividing the spore into two very un- 

 equal parts (PI. XXXVII, fig. 13). One of these, the 

 larger one, contains almost all the chlorophyll-granules of 

 the cell : the other has hardly anything but finely-granular 



* f Bot. Zeit.,'1857, p. 667. 



