50 GENERAL DIFFERENTIATION OF THE PLANT-BODY 



a glass slide, or be attacked by parasitic fungi, or be influenced by other 

 factors unfavourable to its growth. 



The sclerotia of Coprinus stercorarius have a black cortex composed 

 of firm compact tissue. If this be shaved off a new one is formed, and 

 in the case of large sclerotia this may be repeated several times, remind- 

 ing us very much of the formation of wound-cork in the higher plants. 

 A large number of fructifications develop out of a sclerotium and of 

 these one outstrips the others ; if all be removed, new ones arise. If 

 the pileus of a fructification be cut off, a new pileus does not arise 

 from the cut surface, but hyphae sprout from this which proceed later 

 to the formation of a typical fructification. Mycelium grows out from 

 portions cut off from the fructification if they are brought into nutritive 

 solutions ; even the primordia of basidia can grow out again into mycelium. 

 It is quite evident then that fungi behave in respect of regeneration in 

 exactly the same way as do the higher plants ; parts which have been 

 removed are replaced only by ' embryonal ' parts to which of course 

 belong spores, sclerotia, and like structures of which the contents consist 

 essentially of 'germ-plasm,' older parts, which are already differentiated, 

 revert as in the higher plants to the ' embryonal ' state, inasmuch as they 

 grow out into hyphae from which a formation of organs can begin again. 

 The pileus cut off from the fructification of a fungus, or the sporangium 

 removed from the germ-tube of Mucor, can no more be directly regenerated 

 than can a detached flower or a portion of a leaf there is always a 

 vegetative hyphal stage interposed. The fact that a new fructification 

 is formed quicker after the removal of the pileus of a previous fructification 

 than under other circumstances reminds us of the phenomena which have 

 been cited in Begonia and Achimenes ; and it shows that the ' disposi- 

 tion ' which the parts of the plants have acquired is concerned in the 

 regeneration. 



The behaviour of the severed leaves of mosses leads to a similar 

 reflexion. Whilst the leaves of plants which are not in fructification 

 produce easily and quickly new plants indeed these arise from the 

 protonema formed from the leaves quicker than they do on the proto- 

 nema formed in spore-germination in plants which are in fructification 

 such a formation of new plants, according to my experience, does not 

 happen or only occurs slowly after a long time ; and this is so because 

 all the plastic material has flowed out from the leaves to the sporogonia, 

 and perhaps also the plasmic body of the cells has already undergone 

 some not yet visible changes. 



Shoots which have been separated from plants to serve as cuttings 

 retain in general the peculiarities which they possessed. In a fir or a spruce 

 a plagiotropous dorsiventral lateral shoot may grow erect after removal 

 of the terminal chief shoot, and can therefore become radial, and one 



