50 DIVISION I. GENERAL MORPHOLOGY. 



sporophores, as far as they have been observed l , always begin their development as 

 comparatively large compact tufts of hyphae springing from the mycelium, and we 

 may even venture to assume that the great majority of compound sporophores take 

 their origin, as here described, from many hyphae. At the same time it must be 

 acknowledged that it has been found possible to follow them back to their very first 

 beginning with perfect certainty only in the few cases which have been noticed 

 above. 



Many inconspicuous compound sporophores, such as the gonidiophores of Uredi- 

 neae and the stromata of many small Pyrenomycetes, remain as it were in the stage 

 of the tufts of hyphae and pass into their ultimate form without further remarkable phe- 

 nomena of growth. But where a larger structure is produced, the course of development, 

 amid great variety of detail, discloses two chief types, which closely resemble the two 

 types of growth above described, for the mycelial strands on the one hand and for the 

 sclerotia on the other. In the one type, as in the formation of sclerotia, the growth 

 is nearly uniform for a long lime in all parts of the structure; then comes the second 

 chief stage, the ultimate development by internal differentiation. The compound 

 sporophores of the Gastromycetes show this mode of proceeding in the most marked 

 manner. In the other type the general course is progressive* ', just as it is in the 

 mycelial strands or in the single hyphae, advancing in the direction of fixed spots in 

 the surface, which are themselves pioneers in the advancing growth and maintain it by 

 formation of new cells ; as any section becomes removed from these spots growth in 

 it ceases, and its component elements assume their definitive character. According 

 to the form of the whole structure and of the superficial portion of it in which 

 progressive growth occurs, this growth may be said to advance towards the apex, to 

 be apical (acropetal), or to be marginal, and the peripheral progressively growing 

 spots by another usage may be termed growing points or margins ; or growth is 

 progressive towards the whole of the free surface of the structure which bears the 

 hymenium, as in the horse-shoe-shaped pilei of Polypori which are several 

 years old, and in other Hymenomycetes also with various modifications and 

 limitations. 



Growth thus on the whole progressive does not preclude intercalary areas of new 

 formation and extension from making their appearance between portions in which 

 these processes had ceased ; but the actual occurrence of these areas has never been 

 distinctly proved in any of the cases which belong strictly to this type. 



On the other hand, the combination of the two types of growth has been 

 ascertained in a considerable number of species. We find, for instance, internal 

 differentiation and subsequent progressive growth in the compound sporophore which 

 is the chief product of Amanita. The young stipe of the Coprineae 3 has a transverse 

 intercalary zone in the part just below the apex, in which there is continued formation 

 of new cells by (meristematic) division ; the velum also has intercalary growth, but 

 all the growth of the pileus and the final elongation of the stipe is progressive. In 

 the Xylarieae, Cordyceps, &c. the growth of the club-shaped sporophore is progressive 



1 Hartig, Zersetzungserscheinungen d. Holzes, p. 21 (Polyporus annosus), p. 32 (Trametes Pini), 

 p. 41 (Polyporus fulvus), p. 50 (P. mollis), p. 98 (Hydnum diversidens), &c. 

 a Goebel in Arbeiten d. Bot. Instit. zu Wurzbnrg, II, 354. 

 3 Brefeld, Schimmelpilze, III. 



