M. Miiller on the Germination o/Isoetes lacustris. 185 



membrane. At the extremity by which it penetrates through 

 the cellular tissue of the leaf, it appeared to me to end in a pointy 

 while the other portion which extends through the root ended 

 abruptly. The most interesting matter to me in the vessels was 

 the formation of the spiral fibre. The rudiments of this consist 

 of a number of hyaline granules^ which originally have a quin- 

 cuncial arrangement (fig. 21/), but subsequently become blended 

 into rows in the form afterwards presented by the spiral band. 

 I never saw more than three globules in one plane, which was 

 wholly in focus at once beneath the microscope, and comprised 

 about one-half of the utricle of the vessel, and these lay one 

 upon another in various directions. Consequently six of these 

 globules must belong to each turn of the spiral. In my case, as 

 in that of many others, all observations have failed to demon- 

 strate the origin of the vessel. So far as I have seen, the vessel 

 could never be reduced to a cell, since cross septa could never be 

 discovered in it. It appeared to me almost as if the utricle of 

 the vessel, having its origin in the alimentary body or between 

 it and the matrix of the root, went forth at once as an indepen- 

 dent utricle into the leaf and root, for it could not be difficult at 

 this time for it to penetrate through the tissue of the leaf and 

 root, since this was extremely delicate and mucilaginous at the first 

 origin. However nothing definite can be said upon this point. 

 But on the other hand, the origin of the spiral fibre is easier to 

 trace here. It agrees in every respect with what I observed in 

 Selaginellaj and I have nothing further to add upon the subject. 

 Subsequently, when the second leaflet has begun to rise out of 

 the vagina, the vascular bundle divides into two (fig. 22), each 

 of which is composed of two cords. 



3. The First Leaf. — The same events which occur at the lower 

 part of the germinal body, in the root, take place above in the 

 first leaf. The two organs are parallel with each other in many 

 respects. The formation of the vascular bundle is exactly the 

 same here. The cells, too, are at first small, delicate and paren- 

 chymatous, wholly as in the root. Thus they are when the leaf 

 breaks through the coat of the nucleus. The next elongation of 

 the leaf occurs by the expansion of these cells. Thereby they 

 become longer but of a paler green (fig. \7 a), having previously 

 had a very beautiful deep green colour (fig. 16 b). Not until much 

 later does the elongation of the leaf appear to result from the 

 formation of new cells, which in all probability occurs by divi- 

 sion, since we never see a point of vegetation at the apex of the 

 leaf like that of the root. Neither have I observed it at the base. 



There is little to be said concerning the leaf itself. When 

 it has emerged from the ovule, it always has a curved, often a 

 hooked direction. 



An7i. bs Mag. N. Hist. Ser. 2. Vol.ii, 13 



