2l6 



DIVISION II. — COURSE OF DEVELOPMENT OF FUNGI. 



no longer be recognised, so that the perithecium in the mature state is broadly 

 ovoido-conical with an indistinct ostiolc. The wall is formed of three or four layers 

 of not much thickened elongated cells. 



Phyllachora Ulmi appears to show similarity to the process here described. 



ii. The club-shaped stroma of Xylaria polymorpha (Fig. 103) consists in the 

 young state, according to my earlier observations, of a white medulla surrounded 

 by a firm black rind. The former is composed of an air-containing tissue of 

 colourless hyphae ; the rind of the portion bearing perithecia consists of small-celled 

 pseudo-parenchymatous tissue, which is overlaid on the outside by the hymenium 

 which bears gonidia (see section LXXI) and ultimately disappears. The primordia 



FIG. 103. Xylaria polymorpha. A, B, C transverse sections through young stromata with perithecia divided more or 

 less exactly in half, all three magn. 90 times, r rind, in medullary layer of the stroma. A, p very young perithecium cut 

 through the middle, p a similar <<ne cut through near the median plane, q older perithecia, k gonidial layer. J! perithecium 

 with the mouth » bursting through the rind, C a nearly fully developed perithecium ; the section pa esclosi to the mouth, 

 which is fashioned as at </ in A, elsewhere through the median plane ; / the outer, i the inner wall of the perithecium, 

 x the large-celled paraphyses tilling the centre of the perithecium having entirely displaced the short-lived inner ti 

 // the inner surface of the uall with the insertions of the paraphy ;esand asci. 



of the perithecia {A,/>) make their appearance in the form of small spherical bodies 

 which lie in the medulla close beneath the black rind, and are at once distinguished 

 from the medullary tissue by containing no air and therefore being transparent. 

 They are formed of a closely woven mass of slender hyphae, which are much 

 thinner than the hyphae of the original tissue and must therefore be a new formation 

 in it. In somewhat older specimens an irregular large-celled coil of tissue is found 

 lying in the middle of the sphere. The spheres now increase in size in the direction 

 of the medulla, the shape, structure, and position remaining the same. Then a 

 dense tuft of straight hyphae, in the shape of a broad truncated cone, shoots forth from 

 the part which abuts on the rind, and elongates in the direction of the rind, which is 



