69 



in the form of a cylindrical cell, in whose apex (micropyle-end) 

 were contained some small cells. The ovule is pendulous and 

 provided with an integument, the pollinic cell was followed to 

 the micropyle, and here it penetrates the aperture of the in- 

 tegument, expands into an irregular saccate dilatation vary- 

 ing in size, and then passes from thence into the nucleus un- 

 til it reaches the embryo sac : immediately upon this the first 

 trace of an embryo is visible. During this time the cells of 

 the endosperm have expanded considerably until they have 

 reached the chalazar extremity and quite fill it. In these en- 

 dosperm cells he discovered the interesting phenomenon of 

 the rotatory current \vhich existed in each cell ; it was a yellow- 

 ish slimy fluid, intermixed with small globules, which was in 

 motion. The current ascended from the base of the cell, in 

 its axis, resembling an artesian spring, to the very top, where 

 it separated into innumerable, minute^ scarcely perceptible 

 currents, which fell down the sides in all directions, in order 

 to reunite below with the main current. The direction of the 

 central stream is in all cases alike, namely, from the embryo 

 towards the chalaza. 



From the development of the embryo, as also from the di- 

 latation of the lower cells, the upper ones become compressed 

 and die from above downwards. 



The stem of the Ceratophylla consists of bark covered with 

 epidermis, of a ring of bundles of elongated cells, and of pith. 

 The genus Ceratophyllum has no spiral vessels. Dr. Schleiden 

 here remarks that he had discovered spiral vessels in Lemna 

 as early as 1835. However, L. Treviranus had many years 

 ago figured the spiral vessels in the roots of Lemna ; I myself 

 denied the fact, not being able to confirm it with my older 

 microscope, but with the instrument of Ploessl I could also 

 see the vessels. In Zannichellia the spiral vessels are said 

 to disappear in the old articulations. I recollect having seen 

 in the summer of 1835 spiral vessels both in the young and 

 old internodes of this plant. 



Whether the Ceratophylla are perennial or not is not yet 

 ascertained ; they flower from July to the middle of Septem- 

 ber. In the beginning of September flowers and nearly ripe 

 fruit are found on the same stem. The plants contained nearly 

 90 per cent, water, and the ashes f alumina, f silica, &c. 



