64 ALBUGO PORTULAC& OR A. CANDIDA. 



means of sections, requires excellent staining before it can 

 be distinguished. If the material be boiled for one minute 

 in a five per cent solution of potassium hydrate, the tissues 

 may be teased apart with needles and the mycelium exposed. 

 Under high power, with a good dissection or a well-stained sec- 

 tion, observe: 



5. The conidia; exact shape, wall, and contents. 



6. The delicate neck or pedicel supporting each conidio- 

 spore before becoming detached. 



7. Draw a conidiophore with its conidiospores. 



Trace a conidiophore into the tissues of the host plant, 1 

 and observe: 



8. The irregular thickness of the hyphae. 



9. Whether it branches. 



10. Whether partition-walls are present. 



11. The way in which the hyphae apply themselves to the host 

 cells. The specialized organs, the haustoria, by means 

 of which the parasite obtains food from the host cells, 

 are found more readily in the tissues of growing tips and 

 flowers. 



12. Draw, showing hyphae and host cells. 



Dust sonre conidiospores from a fresh growing plant 2 upon 

 a slide and mount with water; 3 in about an hour observe: 



13. The small protuberance formed on one side of some of 

 the conidiospores which opens and permits the escape of 

 the protoplasm in the form of several motile bodies, zo- 

 ospores. 



1 This is not always possible, since the hyphse pass in various direc- 

 tions and many are cut off in making the section. The circular cut 

 ends may easily be seen. 



2 The conidia will germinate if sown at any time of day, provided 

 the specimens are fresh, but will do so more readily when sown in the 

 morning from plants which have remained over night under a moist 

 bell-jar. 



1 Care must be taken that the water does not evaporate, and to guard 

 against this it is best to keep the slide in a moist chamber. 



