Cronartium comptoneae (sweetfern rust) on jack pine seedlings.

Cronartium comptoneae rust showing aeciospores on jack pine.

Cronartium comptoneae rust showing aeciospores on jack pine.

Cronartium comptoniae (sweetfern blister rust) on 2 year jack pine. N.B. aeciospores.

Cronartium comptoniae (sweetfern blister rust) on 2 year jack pine. N.B. aeciospores.

Cross-section of black locust nodule (x360) to show rhizobium cells the bacteria which due the nitrogen-fixation. Alfisol, HF, BSY.

Cross-section of black locust nodule (x4) to show general structure and the red colour due to presence of 'leghemoglobin' which shows there is active nitrogen-fixation. Alfisol, HF, BSY.

Cross-section of dense seedbed (300sdlgs/sq/ft) to show effects of Botrytis mold. Black spruce, 2+0, Botrytis damage.

Cross-section of nodule on Alnus glandulosa showing infected cortical cells (actinomycetes?) stained red; central red tissue are the vascular elements.

Cross-section of seedlings in situ showing lower dead foliage due to Botrytis and dead leadertop to aphids. Black spruce, 2+0, botrytis and aphid damage.