6 Ashworth, Tubers of Anthoceros tuberosus. 



plants which bear tubers, mentioned in the Synopsis, come 

 from Western Australia. We may regard these tubers as 

 gemmae, the inner cells of which have become stored with 

 food materials, and which are protected by a corky 

 envelope formed by modification, when the tuber is fully 

 formed, of the cell walls of the outer cell layers. In 

 Anthoceros tuberosus, we may presume that the internal 

 cellular masses, as well as the ordinary tubers, can give 

 rise to new plants, and hence if the thallus becomes dry 

 and dies there will still remain several living cellular 

 masses, filled with food materials, which will be enclosed 

 and protected by the remains of the dead thallus. These 

 would probably be able to survive a considerable time and 

 then give rise to new plants under circumstances favour- 

 able to their germination. It is possible that this plant 

 forms the cellular masses in the thallus before it produces 

 the stalked tubers, and, thus, early secures protection 

 against extinction by drying during hot periods. That 

 this is a possible explanation is supported by the fact that, 

 in the dry herbarium specimens at my disposal, the 

 histology of the cells of these internal food-laden cells is 

 quite good, and the normal shape of the cells is retained, 

 whereas the ordinary cells of the thallus are shrunk and 

 collapsed. 



The specimens used in this investigation were obtained 

 from the Carrington Herbarium in the Manchester 

 Museum, Owens College, and the work was carried on 

 in the Botanical Laboratory of the College during the 

 Lent Term of this year, under the direction of Professor 

 Weiss, to whom I am indebted for advice and criticism. 



