FEMALE FLOWER-STALK OF VALLISNERIA SPIRALIS. 155 
During the three portions of days constituting this period, the growth was at the rate 
respectively of 1°75, 2:5, and 3:25 in. in twenty-four hours. 
At this stage it seemed possible to measure the rate of growth of different zones of that 
portion of the flower-stalk which, when straightened, was exposed above the surface. 
As, however, neither of the **auxanometers," or instruments for measuring growth, 
described by Sachs in his ‘ Text-book’ can be used for weak stems which do not natu- 
rally stand erect, the only available mode appeared to be to mark off at intervals of time 
measured lengths from the base of the flower-bud. This was done (but necessarily, from 
my engagements, at very unequal intervals) with black varnish, each length of one inch 
being marked off as it rose (when straightened) above the surface of the water, and 
indicated successively as А, B, C, &c., any fraction ofan inch remaining over being added 
to the subaqueous portion. Тһе following table exhibits the result, neither the final 
length attained nor the rapidity of growth being so great as in July, as, indeed, might 
have been expected. 
n B UU B B FF M Н 4 КЕ L NM Бош ТИН. DE 
Sept. 24th, 4 r.m. 1:0 1:0. 87 107 
ДАУА 20: 19 ^ T9 80 119 8 
Ж Ө Жи ЕСІ ЕЕ 19 .. Di OL OM мат ш) 81 1 314 
27,1043. 225 2:5. 1-8 1:0 10 10. 0.10: 10 10.10, ... 88.2995 1096 
2,00xX. 20 27519 L15 115 11 105 POB F0 10.190 10 BL. 2485. 15 
Юри. 27520 20 115 PIGS EFI 14 ri ыы r05 55 2015 25 
oma, Fiw 20 80 21 PIS 115 PIS 146 11 ТҮ Та 11 11 87b Жуда 4 
10 р.м. 31 81 215 1:15 115 115 1:15 1:15 1°15 1:15 1:15 1:15 875 2745 `6 
20th, 9 л.м. 8-25 8:93 2-15 1-15 1-15 1:15 115 1:16 1:15 1:15 1:15 115 88 2775 3 
10 рм. 3:25 3:25 2-15 1-15 1:15 1:15 115 1:15 115 115 1:15 115 88 2775 0 
The general results arrived at are that between 4 р.м. оп Sept. 24th and 9 А.М. on 
Sept. 29th the flower-stalk had increased in length from 107 to 27°75 in., the two zones 
immediately beneath the flower-bud from 2 in. to 6'5 in. This latter portion had in- 
creased during this period 225 per cent., the remainder of the flower-stalk 144 per cent. 
of its original length. | 
The term “ Energy of Growth " of any particular part or zone of a plant is defined by 
Sachs (* Text-book,' p. 741) as *the power of that partieular zone to attain a definite 
length." In the case of the stem of a plant consisting of a number of internodes, the 
measurements of Sachs, Pfeffer, and others show that the greatest energy of growth is 
generally displayed by an internode situated at some distance from the terminal bud, the 
energy of growth decreasing in the successive internodes, both towards the apex and 
towards the base of the stem. Similar careful measurements do not appear to have been 
made of the relative energy of growth of different portions of the same internode. In 
the case of the greatly elongated internode of Vallisneria, the maximum energy would 
appear to be very near the apex, the total energy of growth of the two terminal zones 
being to that of the remaining portion as 225 to 144, or nearly as 3 to 2. The energy 
would appear also, as far as any conclusion can be drawn from my few measurements, 
to decrease towards the base. For, dividing the portion of the flower-stalk excluding the 
SECOND ЗЕВТЕ$. —ВОТАМУ, VOL. I. U 
