UREDINEAE AND HYMENOMYCETES 525 



The existence of the teleutospore in the Uredineae, to which 

 there is nothing to correspond in the Hymenomycetes, is directly 

 connected with the parasitic habit of the fungi concerned. The 

 Uredineae are parasitic upon Phanerogams and Ferns, plants which 

 have regular periods of vegetative development depending on the 

 seasons of the year. The organisation of the Uredineae is perfectly 

 adapted to fit in with this periodicity. And herein we find an 

 explanation of the existence of the teleutospore : the teleutospore is 

 a cell-organ which provides for the rapid production of basidiospores 

 when these can best be liberated with a chance of infecting new host- 

 plants. During summer, the mycelium which is to produce a 

 teleutospore-sorus spends its energies in obtaining from the host 

 tissues the substances which are eventually to be delivered to the 

 basidiospores ; but these substances, instead of being sent straight 

 forward into the basidia and thence into the basidiospores, are 

 packed into the teleutospores, i.e. into probasidia or mother-cells of 

 the basidia, there to be stored until a suitable time arrives for the 

 production of the basidiospores. In Puccinia Malvacearum, this 

 suitable time is the coming of damp weather when the air is saturated 

 with moisture ; in P. graminis it is the spring when the second host, 

 Berberis vulgaris, opens its winter buds and puts forth its tender 

 green leaves. 



Consider now the vernal condition of the haulms of an Oat plant 

 bearing teleutospore-sori of Puccinia graminis. Neither the tissues 

 of the host-plant nor the vegetative mycelium of the parasite are 

 any longer living : only the teleutospores retain their vitality. 

 Yet the teleutospores produce basidiospores successfully within a 

 very few hours after the advent of moist weather. This is rendered 

 possible by the teleutospores being organised as independent struc- 

 tures filled with all the food materials necessary to enable them to 

 develop mature basidia. In being an independent resting body con- 

 taining a store of reserve food-materials and in being destined to 

 produce organs of dissemination 1 under favourable conditions, a 

 teleutospore is analogous to a sclerotium. 



^ I apply the term organs of dissemination to seeds, spores of fungi, soredia of 

 lichens, etc., i.e. to structures which are so organised that they are set free and by 

 the agency of the wind, water, animals, etc., are transported from place to place, 

 so that they disseminate the species. 



