THE TRANSLOCATION OF PROTOPLASM 149 



hymenomycetous fruit-body begins its development, the protoplasm 

 within the mycelium begins to be driven toward it by vacuolar 

 pressure. As the fruit-body rudiment increases in size, more and 

 more mycelial hyphae become highly vacuolated and, as a result, 

 the amount of protoplasm per hour forced into the growing hyphae 

 of the rudiment increases correspondingly. When the fruit-body is 

 growing in size most rapidly, the increase in size of the vacuoles of 

 hyphae in the mycelium goes on most rapidly too, and the rate of 

 flow of the protoplasm along certain mycelial hyphae and into the 

 hyphae of the fruit-body attains its greatest speed, probably at 

 least 10 cm. per hour. As the rate of growth of the fruit-body 

 slows down, so also slows down the rate of flow of the mycelial pro- 

 toplasm into the fruit-body ; and, when the fruit-body ceases to 

 grow, the mycelium ceases to supply it with protoplasm. By the 

 time this stage of development has been attained, the mycelium as a 

 whole or in large part has become fully exhausted and a great many 

 of its hyphae are already dead. 



Thus, in general, a hymenomycetous fruit-body does not receive 

 its nutriment from the mycelium by the slow process of diffusion 

 or by conduction through special persistent channels like sieve-tubes 

 or wood vessels, but in the form of protoplasm forced toward it by 

 vacuolar pressure arising in a system of tubular mycelial hyphae 

 progressively exhausting themselves and progressively dying. 



The growth of the vacuoles in mycelial hyphae engaged in 

 evacuating their labile protoplasm is doubtless due to the protoplasm 

 increasing the amount of the osmotic substances contained in the 

 vacuoles and to the absorption by the vacuoles of more water from 

 the substratum. 



Large vacuoles may be formed in a fruit-body even while it is 

 developing and before it has begun to shed its spores. Thus, in 

 Coprinus sterquilinus, the rapid intercalary growth in length of the 

 upper part of the stipe before and during the expansion of the pileus 

 is correlated with an increase in the size of the vacuoles in the 

 elongating cells. Since there are continuous columns of watery 

 protoplasm stretching from the mycelium in the moist substratum 

 to the most distant hyphae of the fruit-body, including those elon- 

 gating in the stipe just beneath the pileus, the water required to fill 



