. The fungal diseases of the common larch . Larches. 102 HEART-ROT. made very nearly up to the margin, so that in the resting stage the fungus has the appearance shown in fig. 39. A very constant feature of the fructifications of this species is the holes in the sporophores. When the latter encounter a small root or stick, or even a blade of grass, they grow round it, leaving a hole such as those seen in fig. 39. These holes differ from those made under similar circumstances by most other fungi, by being surrounded by a reddish-brown ridge of sterile tissue. This ridge forms one of the most us
. The fungal diseases of the common larch . Larches. 102 HEART-ROT. made very nearly up to the margin, so that in the resting stage the fungus has the appearance shown in fig. 39. A very constant feature of the fructifications of this species is the holes in the sporophores. When the latter encounter a small root or stick, or even a blade of grass, they grow round it, leaving a hole such as those seen in fig. 39. These holes differ from those made under similar circumstances by most other fungi, by being surrounded by a reddish-brown ridge of sterile tissue. This ridge forms one of the most useful features for identification. Fig. 39 shows the appearance of the lower surface of the pores. It wiU be seen that they vary from circular to irregularly oval or elliptical. Their width is usually about 0*25 mm. (=^^ iSoin.), but may be any- thing from 0-15 to 0-6 mm. The pores are not fertile through theii' whole length at the same time. As a fructi- fication grows older the upper part of each pore becomes filled with hyphae, and only the lowermost 1 to 2 cm., i. c. the part nearest the openings, bears spores. During the summer the pores lengthen and the fertile zone moves downwards. Fig. 38 shows the pores in longitudinal section ; two pieces of the fungus are here cut through, in each of which two yeais' growth can be distinguished. In the fertile region cacli pore is lined with the hymenium, a layer made up of basidia _an6. paraphyses. Fig. 41, A, shows this layer as seen in a longitudinal section of the pores. The basidia are 30- 40 fx long and 8-10 /j. broad. Normally each bears four spores (6.), but basidia with two spores are frequent (a.), and basidia with three or five spores On'- Fig. 41.âFames annosus : a, hymeiiial layer inside a pore; a., a young basidiuui with two spores ; &., older basidium with four spores; â p., paraphysis (x200); b, single spore showing attachment to basi- dium ; &., basidium ; St., sterigma ; »e., septum ; sp., basidiospoi-e
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