300 c BOTANICAL GAZETTE [octoser 
OOGENESIS AND FERTILIZATION IN ALBUGO IPOMOBFAE- 
PAN DURANAE. 
(WITH TWO FIGURES) 
Albugo Ipomoeae-panduranae (Schw.) Swingle occurs upon various 
species of Ipomoea, among others the sweet potato, upon which it inflicts, 
however, but slight damage. Its most common host is probably /. paw — 
durata, in which it induces great hypertrophy of leaves, stems, and — 
flowers. The distortions are so marked as to attract the attention of 
even the casual observer. It is within these hypertrophied parts that the 
sexual organs and sexual spores are found in such abundance as to render 
this species the most favorable of all in the genus for the study of oogenesis 
and fertilization. 
The material is killed in admirable condition if cut in pieces a few mill 
meters square (the outer part being first shaved off to avoid endangering 
the knife by adhering sand) and dropped in chrom-acetic acid of the strength 
recommended for other species of Albugo.t The stain chiefly employed 
is the triple stain of Flemming. , 
Inasmuch as several other species of Albugo have been described with | 
considerable care, I will detail here only the more salient features, and those 
which present divergence from the usual types. The early history of coger 
esis runs parallel with that of all other species of Albugo investigate 
namely, the mycelium enlarges to form the oogonium, the nuclei fe 
enlarge greatly, and pass to the spirem condition. This stage presenis 
little divergence from the same stage in other species that it is — 
represented by fig. 45 drawn from A. Bliti.2 Following the stag? 
described comes zonation or the differentiation of ooplasm from pe a 
the ooplasm.3 In A. I pomoeae-panduranae zonation 
character exhibited in A. candida and A. Tragopogomts, M ving 
plasm may be said to fall away from the oogonial wall, gate _ 
only a few strands, sufficient to suspend the oosphere ex: A. Trost Se 
type of zonation is sufficiently illustrated by fig. 27 drawn . 
pogonis.4 
t STEVENS, F. L., The compound oosphere of Albuge 
176, 225-245. pls. 11-15. 1899. (p. 233)- 
2 STEVENS, F. L., doc. cit., pl. 12. 3 STEVENS, F. L.; 
4 STEVENS, F. I.., Gametogenesis and fertilization in Albugo- 
98, 157-169, 238-261. pls. 1-4. 1901. (pl. 3)- 
Bliti. Bot. G47- aur 
loc. cit, Ph 13, figs 
ugo. BOT. Gat. 3 
