478 BOTANICAL GAZETTE | DECEMBER 
Any species grows better in dense cultures than alone, showing that stronger 
individuals grow parasitically upon the weaker. Still stronger individuals 
result when the normal host plants are supplied. The species which have 
the greatest autophytic power have abundant root hairs, while the more fully 
parasitic forms are without them. 
In his second paper Heinricher showed that the Rhinanthaceae require 
light for their development even more than they require a host. Synthesis of 
carbohydrates was shown. by Sachs’s iodin test. Various species of Euphrasia 
differ widely as to their parasitism, some being as independent as Odontites, 
while some absolutely require a host for full development. His third paper 
dealt with Bartschia and Tozzia, the forms which come nearest to holopara- 
sitism. In Bartschia haustoria appear in the seedling stage, there are no 
root hairs, and a bud for the second growth period does not appear unless a 
host is supplied. Tozzia is the most remarkable form of all. It requires the 
stimulus furnished by a host root even for germination, differing in this from 
all other Rhinanthaceae and agreeing with holoparasites like Orobanche and 
Lathraea. For more than a year the plant lives wholly underground as a 
holoparasite, while late in the second season a tiny green shoot appears 
which soon flowers and fruits, Even this plant was shown to have some 
photosynthetic activity, though less than in any other member of the family. 
Bonnier found no active photosynthesis in these plants, and more recent 
authors have been inclined to’ doubt Heinricher’s results. Apparently Hein- 
richer has clinched his case by employing cut shoots and finding synthesis to 
take place there, although he uses the iodin test rather than the more accurate 
method of gas determination. 
In his last paper Heinricher shows that chlorosis depends upon the lack 
of iron in the seed, not upon the more complete parasitism of the individual 
in question, as he at first supposed. In other respects, also, he finds differ- 
ences in the properties of seeds in the same species, showing that all of one 
species do not have the same hereditary characters. Wide individual varia- 
tions are also found to be due to differences of habitat. Strong host plants, 
for example, permit a better development of parasites. Heinricher is inclined 
to explain a number of Wettstein’s species, especially his aestival and 
autumnal species, as true habitat variations. As might be expected, this 
view has called forth a series of polemics® which need not be mentioned 
further, 
Heinricher’s work gives us a basis for theorizing as to the origin of para- 
sitism, since we find every step in the series within one group of plants. 
Apparently root hairs are soon lost, the first demand on the host being for 
raw materials rather than for organized foods, Further parasitism is acquired 
by drawing upon these organized foods, a process which is ultimately followed 
by the loss of chlorophyll and photosynthetic power.—H. C. CowLeEs. 
# Jahrb. Wiss. Bot. 37: 685-697. 1902; 38: 667-688. 1903. Also Oesterr. Bot. 
Zeits. 52: 246-249. 1902; 53 : 205-223. 1903. 
