Cytology of a new variety of A chly a americana . 149 
induced artificially in others by recourse to unnatural methods. 
It appears as if apogamous development were a response of 
the organism to special external conditions. In forms like 
Saprolegnia Thureti, where De Bary after years of experience 
stated that he only once found an antheridium attached to an 
oogonium, it appears that the normal external conditions are 
very favourable to parthenogenetic development and very 
unfavourable for the development of antheridia. We may, 
however, expect to find that even in the case of 5. Thureti 
a complete acquaintance with its conditions of life will enable 
us to secure cultures in which all the oogonia are provided 
with antheridia. The inherent power of producing antheridia 
is proved by the single observation of De Bary. It remains 
for future observers, following in the footsteps of Klebs 
(’9 7, ’98), to determine the conditions of their formation. 
Other effects of the Amputation of Hyphae. If stout hyphae 
are cut off just before sporangium-formation is about to take 
place, and are then placed in a drop of water in a moist 
chamber, with or without a supply of food, the development 
of the sporangium is stopped, and very numerous, thin 
branches appear at all points of the hyphae, and grow out in 
every direction as if seeking fresh supplies of nutriment. If, 
however, the basal wall of the sporangium was formed before 
amputation took place, the sporangium may or may not, 
according to the treatment it receives, ripen and liberate the 
zoospores. When hyphae bearing sexual organs are ampu- 
tated, induced apogamy is not the only result. Young 
oogonia sometimes lose all their protoplasm. They are 
emptied to provide protoplasm for other organs whose 
development goes on unchecked. Occasionally young oogonia 
become converted into sporangia. The end opposite the 
stalk grows out a little, the usual beak-like protuberance 
appears and the spores are ultimately liberated in the 
usual way. 
In other cases, oogonia may return to the vegetative 
condition and produce branches from any point, and these 
generally develop into fresh oogonia much as Humphrey 
