Host Invasion in Systemic Infections of Uromyces Caladii

SUMMARYDormant corms of Arisaema triphyllum are systemically infected with the haploid mycelium of Uromyces Caladii. When growth begins in the spring, leaves and flowers become infected but roots remain free. In the leaf, mycelium is revealed by lesions on the upper surface, from which the percentage of infection may be estimated. The percentage varies from a trace to 100 per cent. In the flower mycelium invades all tissues of the spathe and spadix. Internal pycnia are found in the ovulate flowers, usually 5–8 per ovary and located in the ovary wall (64 per cent), placenta (20 per cent), funiculus (5 per cent), ovule (11 per cent). The mycelium invades the ovule and the young embryo suggesting the possibility of transmission of the disease through the seed.