*2.4. Histological Examination of the Least Pathogenic Fungal Endophyte Seedling Samples*

The results showed that the thin sections stained with lactophenol cotton blue showed the presence of endophytic fungi in the intercellular spaces of *D. nobile* and *D. o*ffi*cinale* seedling tissues (Figure 7). The transverse section of *D. nobile* seedling stems at lower magnification showed dense blue *Trichoderma longibrachiatum* mycelia in the epidermis and mesophyll region (Figure 7A) and, at high magnification, we observed sprinkled colonies proximal to vascular bundles (Figure 7B). The transverse section of the *D. o*ffi*cinale* seedling stem at lower magnification showed *T. longibrachiatum* mycelia in the intercellular mycelia and a lower amount in epidermal region (Figure 7C); at higher magnification, we observed a large amount of *T. longibrachiatum* mycelium in the phloem region with slightly less in the epidermis (Figure 7D).

**Figure 7.** Histopathological examination of *D. nobile* and *D. o*ffi*cinale* stem infected by the least pathogenic test endophytic fungi, *T. longibrachiatum* (ZF05). (**A**,**B**) Transverse section of *D. nobile* stem showing the presence of *T. longibrachiatum* (ZF05). (**A**) *T. longibrachiatum* in epidermal region (10×). (**B**) Dense colonies of *T. longibrachiatum* (ZF05) in phloem with spores (40×). (**C**,**D**) Transverse section of *D. o*ffi*cinale* stem showing the presence of *T. longibrachiatum* (ZF05). (**C**) *T. longibrachiatum* (ZF05) in intercellular mycelia with less in epidermal region (10×). (**D**) Dense colonies of *T. longibrachiatum* (ZF05) in phloem with spores (40×).
