Lecture XII — 167 — ■ Mycotrophic Phagocytosis 



clots are highly refractive, of irregular form, and are very resistant to 

 acids and alkalis. In concentrated H2SO4 they dissolve after a few 

 days, w^hile in KOH they swell somewhat, and on treatment yellow 

 drops appear on the periphery which with osmic acid turn dark brown, 

 indicating presence of fat or oil (Wahrlich, 1886). 



The material brought into the orchid cells has been termed pro- 

 teinaceous, and the hyphae were called "protein hyphae" (Eiweiss- 

 hyphen), but according to A. Fuchs (1924) they are actually glyco- 

 gen hyphae. The breaking down of these hyphae, according to Burges 

 (1939) is due to a loss of vitality. The addition of small quantities 

 of extracts from tubers, stems, leaves and roots of orchids tO' young 

 cultures of the endophytic fungus resulted in all cases in an inhibition 

 of fungal growth and complete decomposition of hyphae within 3-4 

 days, root extracts being much less toxic than those prepared from 

 tubers or stems. Sap of host-cells, withdrawn by means of a micro- 

 pipette and added to blocks of agar smear-cultures produced visible 

 changes within 24 hours, and at the end of four days some empty 

 hyphae could be seen. 



Phagocytosis in Arbuscular- Vesicular Mycorrhizae: — My- 



cotrophy in this sort of mycorrhiza was described by Boulet (1910) 

 from cultivated fruit trees. He said the habit of the endophyte is 

 very constant: Mycelium traverses the piliferous layer, penetrates 

 into cortical cells, ramifies, but seldom penetrates further than % 

 width of the cortex. The endophyte apparently lives upon the starch 

 reserve of the cells which harbour it, for the starch reserve disappears 

 from these cells. In the most internally placed layers part of the 

 hyphae continue development in the cells while another part insinuate 

 themselves into the intercellular spaces, filling the cavities. The my- 

 celium frequently contains reserve. In the region of the endodermis, 

 which is never penetrated, the hyphal wall is partially dissolved and 

 inclusions extravasated. On certain filaments vesicules are abundant 

 and some are intercellular (size 100 /x x 54 jx) while others are 

 intracellular (57 /x x 36 /x). The intercellular hyphae, by a more 

 or less regular dichotomy, form dense coralloid branches called 

 "arbuscles" by Gallaud. The branches often terminate in sporan- 

 gioles which at times are so numerous as to fill the cell cavities. They 

 disorganize rapidly to a granular, somewhat floccose, mass and finally 

 into scattered granules ; or, even more frequently a solid mass is 

 formed and degeneration seems checked. 



Janse, who invented the name of "sporangiole", speaks of them 

 as present in a number of the plants he describes ; e.g., in Dysoxyhim, 

 a member of the Meliaceae, he said the fungus penetrates to the cor- 



