102 
Church . — The Polymorphy of 
At temperatures above 30°, on the other hand ( 30 °- 33 °), 
death occurred sooner or later ; young plants dying in 2-4 
days ; older ones in 4-6 days, dying irregularly in patches. 
This is of interest as showing the unlikelihood of Cutleria 
crossing the Tropics where the maximum surface-temperature 
is above 30°. 
Experiments at low temperatures were not conclusive, 
young plants remaining perfectly healthy after being 
surrounded by melting ice for six days. 
Theory of Sexuality. 
The theory of the sexuality of the Phaeosporeae, which in 
point of fact still remains based on the classical researches 
of Reinke and Falkenberg on Cutleria , and those of Berthold 
on Ectocarpus siliculosus , has more recently been called 
in question by such accurate observers as Kuckuck and 
Sauvageau 1 , who have repeatedly failed in obtaining union of 
gametes in various species of Ectocarpus and allied genera. 
Thus Kuckuck maintains that Ectocarpus siliculosus is 
constantly parthenogenetic at Kiel, and it may be noted that 
Reinhardt has observed both copulation and direct germina- 
tion of gametes in this species at Sevastopol ; while 
Sauvageau in 1895 obtained direct germination in the case of 
the gametes of seven species of Ectocarpus and wholly 
negative results as regards a sexual process. No one, again, 
has ever observed sexual fusion in any of the plants of the 
Giffordia section of Ectocarpus which possess apparent 
antheridia, nor again with certainty in any of the Tilo- 
pterideae. 
The facts in the case of Cutleria , however, appear to point 
to the narrow range of external conditions within which the 
sexual process can be effected : if these conditions do not 
obtain, the plant may fall back on parthenogenesis, which in 
Cf. Ann. de Sci. Nat. 1896, p. 223. 
