Systematics and Evolution, Part A The Mycota

Fig. 3.12Morphology of Rhipidiales.(a–c) Drawings
ofAraiospora pulchra. Mature tree-like thallus showing
fine basal hyphae and terminal branches bearing both
sporangia and oogonia (a). Wax-embedded section of
newly fertilized oosphere (b) showing periplasm sur-
rounding a developing oosphere. Mature oospore with
multilayered scalloped wall (c). (a) Adapted from Spar-

row ( 1960 ), (b) from King ( 1903 ), and (c) from Dick

(1973a) after Shanor and Olive ( 1943 ). (d) Sporangium

ofRhipidiumshowing vesiculate release of zoospores.

From Sparrow ( 1960 ) after Thaxter ( 1896 ). (e) Differ-

entiating oospores ofSapromyces elongatusshowing

septate constrictions delimiting both oogonia and

antheridia. From Dick (1973a), with permission

Fig. 3.13 Morphology of Albuginales.(a–h) Drawings
ofAlbugo candidainfectingCapsella bursa-pastoris.
Section of a sporulating pustule showing chains of
conidiosporangia and displaced epdidermis (a). Eucar-
pic hyphae with small globose haustorium (b).
Sequence showing vesiculate discharge of zoospores

from mature sporangium (c–e). The free-swimming

zoospores are rather rounded (f). Mature oospores

showing thick verrucose wall (g) and direct vesiculate

release of zoospores upon germination (h). All from

Webster ( 1970 ), (h) based on Vanterpool ( 1959 )

66 G.W. Beakes et al.