41 



INOCULATION OF WATER PLANTS. 



As a concurrent sui^plement of the above described infection by wind and by insect^, 

 water must further be added as a medium and means of infection with smut fungi, which should 

 l)e taken into consideration in separate cases. The forms of Doassansia inhabit mostly the 

 leaves of water plants ; for example, Alisma, Sagittaria etc., and develop in these strongly local- 

 ized pale spots, in which may be found the threads of the parasite and, especially at the end of 

 development, the large peculiar masses of spores by which the Doassansia forms are charac- 

 terized. . These spore masses consist of fructificative forms only in the inner cells. The outer 

 si)orc layer is sterile and forms an envelope about the inner spore mass, which thus appears as 

 a morphological entity. These enveloping cells lose their contents in time. These are replaced 

 by air and, when this has taken place, the outer spore-layer becomes a floating apparatus. The 

 spore masses germinate in water like Tilletia\ They produce hemibasidia from the separate 

 spores of any mass, on the tips of which, like little heads, is produced a number of conidia. 

 These continue their budding directly and form many filiform bud conidia, both when nour- 

 ished in nutrient solution and also in water which is not too poor in organic substances. The 

 conidia are formed in great masses. They are separated from the filiform bud colonies into 

 distinct members, which are distributed in the water and can continue their budding even on 

 the ujiper surfaces. The conidia evidently reach the young leaves which are still submerged, 

 penetrate either under the water or on its surface into these young leaves and, when they are 

 entirely matured and somewhat raised from the water, develop in them the characteristic pale 

 places which betray the presence of Doassansia in the leaves. It is also conceivable that Doas- 

 sansia conidia reach the mature leaves which are already above the surface of the water. It 

 is, however, not probable that they can penetrate into the already matured and hardened tissues 

 of the leaves. This penetration is limited rather to the meristematic tissues of the plant parts 

 which may l)e infected, as in all cases of smut fungi. These are the young and immature leaves 

 which in Sagittaria and Alisma are still submerged. 



We may say that infection takes place here by means of water, since it is at least very 

 much limited outside the water in the mature tissues of the leaf and perhaps does not occur 

 at all. We must not exceed here a brief mention of the noteworthy infection of host plants 

 of the Doassansiae lest we anticipate the further results of investigation also for the forms 

 of smut fungi living in water-plants; for Ustilago longissima, which produces spore masses in 

 the leaves of Poa aquatica, and also for Ustilago grandis, which grows in brackish water on the 

 axis of Pragmitcs communis. It is probable that the infection of the germinating seedlings takes 

 place successfully in floating media and that the germs of infection distributed from the spore 

 masses through the water reach the young seedlings and attack them. The sm^ut spores are 

 germinated in both cases with hemibasidia, which, according to their formation, were not as yet 



(1) See Part XII of this work, plate XII. 



