1897.] Vegetable Physiology. 719 
Mr. Miyoshi finds that within certain limits it is the difference in the 
concentration of the chemotropic substance in two layers rather than 
rE ae ° e Nee , ~x ad S k A ` r “ne 2s s * 
e ia par bs * mii tien T ee i 7 wa k" ` a he A at ure K 
r SL eae of A fag EA p02 902 8 AS i Ta wS, ewt e.,] 
ER Sa GELS 5 ‘Ge, Oe Ge pt g a Pi J "4 o Ove ey oe My 
fate Ve ae GE C = me Ce le {wh ute ae th! vat t e “g t a aS “ot 
ay oy at ee ee afr ` ’S BoE s` NE IR 2 ies y R eag 7° 
' v ae ie = 4 © x Nig & a 7 = owe ae ae mil 4 
4 
SQ es 
Fig. 2. 
the amount of concentration which controls movement. Positive 
chemotropism gradually disappears as diffusion renders the concentra- 
tion slight. The concentration difference must be 1:10 or more to in- 
duce decided turning. If the concentration is great, negative chemo- 
tropism is apt to set in, e. g., Mucor mucedo shows strong, positive 
chemotropism to 2 per cent. cane sugar solution, it is feebly positive 
with 0.1 per cent., while with diluter solutions the fungus does not re- 
act; with solutions stronger than 2 per cent. the positive reaction in- 
creases up to 10 per cent., and then slowly decreases at 15, 20 and 30 
per cent., becoming negative at 50 per cent. We reproduce one of 
Mr. Miyoshi’s figures showing the movement of the germ tubes of 
Saprolegnia ferax into a puncture in a collodium plate through which 
2 per cent. meat extract was diffusing. Hyphae inside the circle of 
diffusion always turned their growing point toward the zone of higher 
concentration and finally entered the opening where it was strongest. 
Identical results were obtained in light and dark rooms. The experi- 
ments seem to have excluded heliotropism, geotropism and all move- 
ments due to simple contact. 
Pfeffer’s capillary tubes in water or 
very dilute nutrient solutions under 
cover glasses were also used, but this 
method, while giving some interesting 
results, is stated to be better adapted to 
motile organisms. Many substances 
were found to attract, and a long list is 
given with the behavior of the six fungi 
first mentioned toward different concen- 
Fig. 3. trations. Among the strongly attract- 
i e | GOs : Q 
PAmMmNnaimIn 
phosphates, meat extract, peptone, sugar, dextrin, asparagin, ete. The 
