M. Miiller on the Germination of Isoetes lacustris. 91 



The slight bend becomes continually more evident. A growth 

 toward different sides visibly commences, showing itself in the 

 altered form of the embryo ; this is now elongated distinctly 

 upward and downward (fig. 11). On the former prolongation 

 nothing more is seen, except that the upper part of the embryo, 

 i. e. that which subsequently breaks through the ovule, becomes 

 attenuated. The alteration which occurs in the lower portion 

 is more important. A growth toward two different sides mani- 

 fests itself in very delicate outlines. On the one side (fig. W a) 

 the embryo bulges out, on the other {b) it is attenuated, and the 

 most external of the cells project spherically beyond the surface. 

 Meanwhile a solitary cell in the concavity of the embryo has be- 

 come so much enlarged that it protrudes like a globule beyond 

 all the rest (fig. 11 c). This is the first cell of the future so-called 

 scale. This exhibits over again all the phsenomena presented by 

 the mother-cell of the entu'e embryo. It contains like the latter 

 an almost transparent, extremely tine granular cytoblastema, and 

 is itself of an extraordinarily delicate structure. It is, moreover, 

 situated in a fold, which is more clearly seen in the figures 12 

 and 13. This fold is the future furrow or channel of the leaf 

 When the observer succeeds in getting a view of this fold on the 

 direct face, it is distinctly seen that the mother-cell of the scale 

 stands upon another cell which serves for its foundation, and 

 projects in like manner beyond the other cells forming the sur- 

 face. I now leavfi the cell of the scale, that I may hereafter ex- 

 amine it more minutely in its relations as an independent organ, — 

 the Scale. 



While the cell of the scale up to the stage in fig. 13 has in- 

 creased in size only and shown no apparent alteration in its in- 

 terior, the double growth of the lower portion of the embryo has 

 manifested itself in a more distinct manner ; the projecting por- 

 tion has become more evident, and the terminal cells forming 

 spherical projections from the surface of the opposite side now 

 have a horizontal direction. 



This soon alters. The projecting portion which before only 

 bellied out now becomes conical (fig. 12 a), Meanwhile it may 

 be perceived that the lower surface of the embryo is becoming 

 curved, at first slightly, afterwards in a very marked degree. 

 Then that portion of the embryo on which the spherical, pro- 

 jecting cells occur turns upwards, out of its horizontal position 

 and thus acquires one more vertical. By this means the sphe- 

 rical cells come to be placed on the upper surface (PL II. 

 fig. 12 d). Here they come into immediate contact with the fold 

 (fig. 13c), the furrow of the future leaf, surround the mother- 

 cell of the scale like a semicircular wall, atid form thus the foun- 

 dation of the future leaf -sheath of the second leaf. 



