3<D2 Journal of Agricultural Research vol. xx. No. 4 



to produce endogenous motile bodies resembling zoospores that later 

 escaped through a number of openings on the distil side of the vesicular 

 wall. As the Van Tiegham cultures in which this process was noticed 

 were usually several days old, the development of bacteria and various 

 protozoa brought into the observations a considerable measure of un- 

 trustworthiness. Indications that similar contaminations may have 

 affected the observations of Wilson (37) on Urophlyctis alfaljae and of 

 Bally (2) on U . rilbsaameni are not entirely wanting. Both of these 

 writers describe the resting spore as functioning directly as zoosporan- 

 gium. 1 



PENETRATION OF THE HOST 



Because of difficulties encountered in efforts to bring about infection 

 under artificial conditions, it has not been possible to observe directly the 

 penetration of the host by the germinating zoospore. However, as an 

 abundance of conditions immediately following the entrance of the 

 parasite were found in stained sections of buds, the course of events 

 during the time of invasion can be followed in incipient stages in the 

 same manner as during advanced stages. 



Bodies measuring 3 to 4 n in diameter were frequently found attached 

 or adhering to the scales or developing axis of the bud. They appear to 

 have made their way under the bud scales very close to the most rapidly 

 growing meristem. Unfortunately, no clear figures showing the immedi- 

 ate development of these bodies were observed — a failure attributable 

 apparently to the fact that by the time the galls became noticeable 

 many weeks had seemingly elapsed since the period during which infection 

 took place abundantly. As a result, the earliest demonstrable stage of 

 invasion was represented by the presence of small turbinate bodies (the 

 "Sammelzellen," "corps centrals," "vesicules collectrices," or "vesi- 

 cules collectives" of other writers) within the epidermal cells of the outer 

 foliar or scale elements of buds exposed to attack, and attached to and 

 perforating the cuticular wall by an elongated beak (PI. 49, A, ta-tg). 

 More than one body may be present in the same epidermal cell, two or 

 three being not unusual; and occasionally a considerable number of 

 contiguous cells may show such evidence of multiple and concentrated 

 attack. The beak manifestly represents the tube proliferated by the 

 zoospore through which the contents of the latter were conveyed into 

 the host cell after the manner prevailing very generally throughout the 

 Chytridiales. 



1 In an article that has appeared since this paper was prepared, Wilson {38) gives a more detailed ac- 

 count of his findings. So far as his account concerns the germination of the resting spores, it appears to 

 differ very considerably from that more recently published by C Emlen Scott (30), according to whom 

 each resting spore proliferates from 1 to 15 sporangia, the zoospores escaping through a number of tubes 

 in the hyaline wall. With the latter account the observations recorded above are not at variance. 



