198 



Methods in Plant Histology 



from the swollen end of the hypha to the ripe spore (Fig. 53). Per- 

 manent preparations of the conidial stage, as shown in Fig. 53, and 

 also of the coiled twisted filaments which initiate the ascosporic stage, 

 should be made by the Venetian turpentine method or by the glycerin 

 method. 



Fix in 1 per cent chromo-acetic acid (1 g. chromic acid and 1 c.c. 

 acetic acid and 100 c.c. water) for 24 hours; wash in water 24 hours; 

 transfer to 10 per cent glycerin and continue the Venetian turpentine 

 method. 



Material may be fixed in corrosive sublimate acetic acid (cor- 

 rosive sublimate 2 g., glacial acetic acid 2 c.c., and water 100). Use 



B 



FIG. 53. Aspergillus: from material growing on a hectograph pad; fixed in chromo- 

 acetic acid, stained in eosin, mounted in glycerin; A-E, successive stages in development. 

 X375. All such material is more satisfactory when mounted in Venetian turpentine. 



it hot (85 C.) . One minute is long enough. Wash in water and add, 

 a few drops at a time, the iodine solution used in testing for starch. 

 At first, the brownish color caused by the iodine will disappear, but 

 after a certain amount has been added the brownish color will remain. 

 Stain in eosin or iron-haematoxylin. and follow the Venetian turpen- 

 tine method. 



A very rapid method for this and for similar small filamentous 

 forms may be added. Forms as large as Thamnidium elegans can 

 be mounted successfully by this method. 



1. 100 per cent alcohol, 2 minutes. 



2. Eosin (aqueous), 2 minutes. 



3. 1 per cent acetic acid, 2 to 10 seconds. 



4. Wash in water 5 minutes, changing frequently. 



5. Mount directly in 50 per cent glycerin and seal. 



