216 Dr. W. Pringsheim on the Germination 



known cellulose reaction^and therefore offers a strong support to 

 the opinion that the cellulose reaction is only prevented in mem- 

 branes which do not exhibit it, by a matter infiltrated in them. 

 In one case the infiltrated matter may be detected even by its 

 colour, and after the removal of this substance the membrane 

 reacquires, with the ordinary colourlessness of vegetable mem- 

 brane, the chemical characters of cellulose. 



After the transformation of the contents is terminated and 

 the formation of the inner two membranes completed, the ger- 

 mination of the spore commences by a growth of the internal 

 cell formed by the inmost membrane. The increasing size of 

 the internal cell first causes the yellow membrane to break across 

 in an irregular crack (PI. VIII. fig. 1 a), and after a further 

 growth of the germinating cell, the outer colourless membrane 

 tears in a similar manner. This succession of the bursting of 

 the outer coats of the spore is caused by the structure of the 

 spore and the unyielding rigidity of the middle coloured coat. 

 The internal cell, bursting forth from the coats, grows in the 

 course of a few days into a longish cell, which soon presents 

 septa and becomes a many-celled filament, which resembles the 

 parent, both in the number of spiral bands and in dimensions 

 (PI. VIII. fig. 1 c)*. Even in the unicellular condition, one end 

 of the cell is elongated in a tubular form (fig. 3). The green 

 spiral bands do not extend into this, always unbranched, radical 

 extremity, and its further growth being restricted, it remains 

 fixed from an early epoch, at that stage of development which 

 it has attained in the young, few-celled plant, while the opposite 

 end of the spore is capable of unlimited elongation by unin- 

 terrupted growth and repeated formation of septa. 



This differencing of the two ends of the spore, expressed in 

 different directions of growth, and the limited growth of one 

 and the unlimited growth of the other, occur indeed — with the 

 very rare exceptions when both ends are characterized by un- 

 limited growth — in all spores ; but a difference is found in 

 them, that while, in most, that end of the spore-cell which 

 emerges first out of the coats (figs. 1, 3, 3, 10), is converted 

 into the cellular Spirogyra-^Xament, and the end remaining in 

 the coats grows out into the radical tube, in other (less nu- 

 merous) spores, their two ends behave in exactly the opposite 

 way, the cell-forming end remaining behind in the coats (PI. IX. 

 fig. \\ a, b, c), and the radical extremity making its way out of 



* Hence the characters derived from the number of the spiral bands, 



and the dimensions of the filament-cells appear to have a specific value ; 



at all events these characters are propagated by germination. Compare 



also Vaucher's figures of the germinating Spirogyra with those of the 



■ parent plants. 



