1048 REPORT— 1898. 



some months to traverse its dormant tissues during the winter and spring. A 

 spotted tuher may give rise to some healthy and some diseased sprouts, according 

 to the tracks of the fungus. 



A curious phenomenon was observed in some potato-plants very badly attacked 

 by this^ disease this summer. In some of the badly diseased young shoots 

 quantities of beautifully developed cubical proteid crystals (crystalloids) were 

 observed in the parenchyma of the pith and cortex. It is due to Mr. W. G. P. 

 Ellis to point out that he was the first to see these in some sections he was kindly 

 cutting for me of this batch of specimens. On going further into the matter Ifind 

 such crystalloids have been seen by Heinricher in the shoots of a diseased potato/ 

 but he did not give any account of the disease itself. 



I find these crystals are not uncommon in the still green bases of the petioles of 

 the withered leaves hanging on the diseased shoots, though they do not always 

 occur. 



I ascribe their formation to the accumulation of proteids in the leaves, while 

 still living and active, from which the passages of transference at the nodes of the 

 stem have been cut off by the fungus ; just as the eventual withering of the leaves 

 is due to the blocking of their water-conduits when all the vessels are stopped up. 



At the same time, the attempts I have made to induce the formation of these 

 crystalloids artificially have failed so far. 



Neither ringing, nor ringing combined with destruction of the pith with a hot 

 skewer — to destroy the internal phloem — has given satisfactory results as yet, 

 though the leaves of healthy plants withstand this drastic procedure much better 

 than might be supposed. 



Here again I must reserve further particulars for the fuller paper. 



In conclusion, it is evident that the efforts of the potato-grower must be directed 

 to the selection of sound sets, and to the careful preparation of his ground. I hope 

 to show later that it is a fatal procedure, even with sound sprouts, to allow the 

 young shoots to lie in contact with raw manures, as it is via wounds and small 

 rotting spots at and near the collar that new infections occur. The same arguments 

 apply to wet soils and situations, and the disease is particularly apt to increase 

 when wet and cold weather supervenes on the early growths. 



5. Penicillium as a Wood-destroying Fungus. 



By H. Marshall Ward, D.Sc, F.R.S., Professor of Botany in the 



University of Cambridge. 



Spores from pure cultures oi penicillium were sown on sterilised blocks of 

 spruce-wood, cut in March, and were found to grow freely and develop large 

 crops of spores on normal conidiophores. Sections of the infected wood showed 

 that the hyphfe of the mould entered the starch-bearing cells of the medullary 

 rays of the sap-wood and consumed the whole of the starch. The resin was 

 untouched. In culture three months old the hyphfe were to be seen deep in the 

 substance of the wood passing from tracheide to tracheide via the bordered pits. 

 Control sections, not infected and kept side by side with the above, contained 

 abundance of starch, and no trace of hyphae could be detected in them. 



The observation appears of interest in several connections. Penicillium is one 

 of our commonest moulds, and undoubtedly plays a part in the reduction of plant 

 dibris to soil-constituents ; how far it can itself initiate the destruction of true 

 wood, or how far it merely follows on the ravages of other fungi, bacteria, &c., is 

 unknown. There are strong grounds for believing that it destroys the oak of 

 casks, &c., but since these are impregnated with food-materials this is not very 

 surprising. Trabut - has shown that penicillium will grow in solutions containing 

 2-9'5 per cent, of CuSO^, and other evidence exists showing how remarkably 

 resistant this mould is, and how little organic matter it needs for life. 



' J5er. d. deutsch. hot. Ges. 1891. 



* Bull, de la Soc. Bot. de Fr., xlii., 1895, 1. 



