432 Prof. H. Marshall Ward. The Relations between 



of the flowers, especially the stigmas and anthers, by means of spores. 

 After growing ontside the organs for some time, the hyphee — now 

 invigorated by their saprophytic nutrition — were able to enter other 

 tissues, e.g., those of the leaves, pedicels, &c. Experiments were then 

 tried with Echeveria metallica* with complete success, and it may be 

 remarked that this disease is very common in a sporadic form on 

 Crassulacae in green-houses. Infections of Lilium were also successful, 

 and Hemerocallis flava was destroyed with extraordinary rapidity. 

 Many other plants were also infected successfully. 



In all these cases the spores only infected (directly) the most delicate 

 or least protected parts of the flower, but the resulting mycelium 

 when invigorated by its growth in the dead tissues was capable of 

 directly infecting, the ordinary tissues of plants. 



It will be remembered that de Bary came to a similar result with 

 his experiments,f and I have observed the same phenomenon over 

 and over again with several of these forms. There is one, for in- 

 stance, which sometimes cases great havoc among snowdrops in the 

 early spring, and I found that the infection occurred especially by 

 means of small invigorated mycelia developed from spores which ger- 

 minated on the dead tissue of the sheaths at the base of the leaves ; 

 these hyphse easily penetrated into the etiolated bases of the leaves 

 and young flower-buds, especially when the plants were partially 

 buried in snow. J Similarly with oifions, hyacinths, and other plants ; 

 and similarly in every greenhouse on plants too far from the light, 

 and often in store cellars on etiolated geraniums, calceolarias, and 

 other plants put by for the winter. 



But a still more remarkable proof of the influence of nutrition on 

 the fungus is shown in the recent discovery that the conidia of suc- 

 cessive generations of the Botrytis have different powers of infection. 



, It has already been pointed out that the conidia may or may not 

 directly infect the tissues, and that one set of events affecting this is 

 the condition of the tissues themselves : another, however, is the kind 

 of food-materials on which the mycelium is growing which yields the 

 conidia. I have found that if the attempt is made to infect a carrot 

 with conidia taken directly from the Botrytis growing on artificial 

 solutions it often fails, whereas the conidia produced on the carrot as 

 a substratum succeed more easily; moreover, there was so much 

 variability in the infections, and especially in the rate of progress of 



' * N.B.— This is one of the plants which is particularly rich in organic acids, and 

 shows well the influence of warmth and daylight in diminishing them (see 

 Warburg, loc. ext., especially pp. 125, 132, 133, 134). 



f 'Bot. Zeitg.,' 1886, col. 396 (see also the remark under Sclerotinia FucJceliana 

 in ' Comp. Morph. and Biol, of Fungi,' p. 380). 



% A circumstance distinctly calculated to retard the decomposition of the acids- 

 and to bring about a tender etiolated condition. 



