138 ON THE FEMALE FLOWER-STALK OF VALLISNERIA SPIRALIS. 
This flower-bud was first observed at 10 А.М. оп Sept. 22nd, when its apex was 1 inch 
below the surface. Ву 9 А.м. on the 23rd, the total length of the peduncle was 9:75 ір. ; 
at 8.30 a.m. on the 24th, 13:95 in. ; 8.30 a.m. on the 25th, 16:6 in.; 10 А.М. on the 27th, 
19:0 in. ; and at 9 А.М. on the 28th it had reached its ultimate length of 19:75 in. Two 
terminal zones, together 1:6 in. іп length, were first marked off at 6 Р.М. on Sept. 23rd, 
and had finally, at 9 a.m. оп Sept. 28th, attained the length of 3:6 inches, or had 
inereased 125 per cent. on the original length. Тһе remainder of the stem had during 
the same time increased from 10 in. to 16:15 in. or 61:5 per cent. The total energy of 
growth of the terminal portion was therefore in this instance just double that of the 
remainder; but the latter had undoubtedly been checked by the accidental injury. 
Тһе flower-bud, when it fivst rose to the surface of the water in the aquarium, was 
‘Sin. in length, and closely enveloped in its spathe, from which it shortly afterwards 
gradually emerged, but did not open until the growth of the flower-stalk was nearly com- 
pleted, when it had attained a length of "75 in. Тһе flower remains open floating on the 
surface for weeks, with the stigmas in an apparently receptive condition. Ву the time 
its growth is completed the flower-stalk has become very wavy, but does not coil up in 
shallow water when the flowers are unimpregnated. 
Тһе only record I have been able to find of observations on the rate of growth of 
different portions of the same internode is by J. Münter, in the first volume of the 
* Botanische Zeitung’ for 1843. Не here lays down the general law that in the inter- 
nodes of dicotyledonous plants the energy of growth, or, аз he terms it, the vis procreativa, 
increases from below upwards, or may be described as centrifugal. This result he 
found most strikingly displayed in the peduncle and pedicels of Pelargonium, the 
only observations, I believe, which have hitherto been made on different parts of indi- 
vidual internodes *. It is interesting to compare this with the law of growth of stems 
taken as a whole, which is thus laid down by Sachs (* Text-book,’ p. 740) :—“ As it is 
usual for several contiguous internodes of stems to be growing at the same time, and the 
maximum rapidity of growth occurs, according to circumstances, іп the 2nd, 3rd, 4th, 
or 5th internode beneath the bud, the region of most rapid growth is at a considerable 
distance from the apex of the stem, and especially when the internodes attain a con- 
siderable length and several are growing at the same time. Іп roots, оп the other hand, 
the maximum rapidity of growth occurs much nearer the punctum vegetationis, usually 
at a distance of only a few millimetres.” It would appear, therefore, as if the phenomena 
of growth in the flower-stalk of Vallisneria exhibit a closer similarity to those of the roots 
than of the aerial stems of terrestrial plants. 
* See also the reference to Miinter’s observations on the Hyacinth, postea, p. 143. 
