530 
ADRIAN J. PIETERS 
the foundations laid by Klebs and the present writer believes that the 
proposition that the succession of forms in the development of any 
plant is conditioned by environment, needs no further support than 
that furnished by the work of Klebs, Vochting ('oo), Kauffman ('08), 
Freund ('08), Obel ('10), and Raciborski ('96). 
It has seemed worth while, however, to answer a question raised 
in the writer's mind by a study of Klebs's paper on Saprolegnia mixta. 
In this paper Klebs describes the production of sporangia and oogonia 
on a mycelium transferred from one solution to another, and states 
that such a mycelium, to react properly, must have been '^well nour- 
ished." He does not define more exactly what he means by this term. 
Obel ('10) also emphasizes the need of a vigorous mycelium and uses 
a solution of peptone, sucrose and salts instead of the pea extract 
favored by Klebs. Obel agrees with Freund ('08), who states that, 
in algae, the conditions favoring the production of reproductive bodies 
depend upon the preceding conditions of growth and Obel states that 
this conclusion is confirmed by an examination of the Saprolegniaceae 
('10, p. 427). Freund does not, however, give the results of any 
experiments to show the importance of the vigor of growth in the 
algae, and apparently makes the statement as a general one, meaning 
that the alga must be in good health and not in poor condition. 
Neither Obel, Klebs nor Kauffman gives any record of experiments 
on this point. In his paper on 5. mixta ('99) Klebs repeatedly refers 
to the necessity for a well nourished mycelium and states (p. 585) 
that during vegetative growth a part of the nutritive substance is 
stored, to be used later when reproduction shall have commenced. 
Further on the same page the statement is made that the production 
of oogonia requires a nutritive plasma (Nahrplasma) of a somewhat 
different composition from that needed for the production of sporangia. 
Klebs fully recognized that the chemical nature of the solution to 
which a mycelium is transferred, is important. He found that 
haemoglobin and leucin were the substances most favorable to the 
production of oogonia and that the addition of certain phosphate salts 
increased both the number of oogonia and of antheridia. Kauffman 
('08), in his work with 5. hypogyna and with two cultures of S. mixta, 
did not find any marked increase in the number of oogonia due to the 
addition of salts, and the number of antheridia in the case of S. 
mixta was as marked in the solutions containing magnesium sulphate, 
as in those containing phosphates (1. c, p. 368). However, neither 
