iQoS] CURRENT LITERATURE 



203 



NOTES FOR STUDENTS 



Regeneration in mushrooms-— By a series of experimental studies on the 

 regeneration phenomena in mushrooms, Magnus "has attempted to analyze the 

 principles underl}'ing the organization of the complex fruit-bodies of tliese plants. 

 It was found that the cultivated mushroom, which was chiefly used in the 

 experiments, possessed a marked capacity for regeneration, which varied with 

 the age of the fruit-bodies and with the character of the tissues involved. In 

 extremely young fruit-bodies, w^ounds caused by removing sections are quickly 

 nlied up by the growth of new tissue, but with increasing age this power of regenera- 

 tion gradually disappears. The most extensive changes occur when a piece ot 

 the pileus in slightly older stages is removed by a perpendicular cut. The wound 

 soon becomes overgrown with a sort of wound tissue, which is covered with an 

 irregular hjTuenium consisting of sinuous lamellae or spines or irpex-Hke plates, 

 ail intermingled. The hymenium arises without reference to graWty, but it 

 always originates in contact with the old h}Tiienium and then gradually spreads 

 over the normal tissue. Although the reticulations of the new hymenium arise 

 Without order, there appears a certain definite regularity in their relation to each 

 other, so that whatever their form may be they always remain at definite dis- 

 tances from each other. It appears that the whole surface is capable of pro- 

 aucmg lamellae, but by some chance advantage certain portions start first, and 

 these then exert an inhibiting influence over a given area and prevent the forma- 

 tion of new growing points, which would cause the lamellae to be too much 

 crowded. In the normal expanding pileus the lamellae appear to be formed 

 according to the same principles; for when the first-formed lamellae become 

 separated by the growth of the margin of the pileus, new ones are interpolated 

 among them, keeping the number per unit of space constant. 



Besides the typical regeneration of parts, various tissues of the mushroom 

 have the power of vegetative sprouting. In the youngest stages all hyphae return 

 readily to a condition of vegetative growth; mth increasing differentiation, how- 

 ever, this power is lost to a great extent. The paKsade cells of the h}'menium 

 and the cells of the cortex soon lose their capacity for vegetative budding, ahhough 

 some of the cortical cells in the lower part of the stem later re^n this power. 

 In general it appears that the most highly specialized cells are the fiist to lose 

 their capacity for returning to the vegetative condition. These facts argue m 

 favor of a progressive differentiation of the hj-phae which make up the fruit-body, 

 and is opposed to the dew that the character of the hyphae is largely determined 

 hy tropisms dependent upon their position in the fniit-body. If the character 

 of the h\*phae were merely a fimction of their position in the fruit-body, we should 

 fi-'^pect all hyphae to return readily to the vegetative stage. On aca>unt of this 

 character of progressive differentiation toward a determinate form, the author 

 ^gards the fruit-body of higher mushrooms as a definite entity, resembling in 



"i 



ilAGNTis, Weelxer, Uebet die Formbildunsc der Hutpiize. Archiv, 



tologie 1:85-161. ph. 8-13. 1906. 



