324 BOTANICAL GAZETTE [NOVEMBER 
the nature of the effect of the clinostat is correct, as shown by 
Firtinc’ and others, but the assumption that this experiment 
proves it is quite another question, and, as we shall show later, 
quite out of accord with a number of other facts. 
Nott’ mentioned the fact that Francis Darwin’s conclusion 
that gravity is a direct stimulus in determining the lateral distri- 
bution of the peg is not proved by his meager experiments. He 
also claimed that only 50 per cent or less of the seedlings grown 
on a Clinostat produce ringlike pegs, while the remainder show 
sharp arching, with a one-sided peg. Nott stated that all flanks 
of the hypocotyl are qualitatively equally capable of peg-develop- 
ment, but that quantitatively the broader flanks produce the larger 
peg. He concluded that contact of the seed coats is not a necessary 
stimulus to peg-development, for the peg still appears when the 
coats are removed. The contact of the coat, however, increases 
the size of the peg. He performed a number of experiments in 
which seeds were germinated with the two opposite broad faces 
exposed to gravity alternately and for equal periods. In all these 
cases the two faces developed essentially equal pegs. He especially 
emphasized these as showing that the peg stands in strong rela- 
tion to gravity and owes its stimulus for formation to gravity. 
Many experiments were also performed in which seedlings were 
grown with the radicle directed perpendicularly downward or at 
a slight deviation from this position. From these he concluded 
that the gravity stimulus reaches beyond the lower pole of the 
seedling axis. At a deviation of 5° from the vertical he found a 
weak peg on the upper side, while at 725 the peg was almost 
exclusively on the lower side. He fixed the limit of the field of 
stimulation at 6°-8° deviation from the vertical. He specified 
that these are to be taken only as approximate figures and as 
applying to Cucurbita Pepo. In two seedlings slight pegs — 
found on the upper side at a deviation of 8°. Seedlings were also 
found that showed no peg, but he did not know how to account 
for this. On account of great variation in response, NOLL empha- 
7 Frrrine, Hans, Jahrb. Wiss. Bot. 45:575—600. 1909. 
‘Nott, F., Zur Keimungs- Physiologie der Cucurbitaceen. Landwirt. Jabtb. 
30:145-165. roor. 
