424 PROTECTION AGAINST PLANTS. 



yeast, or of elongated cells termed liypliae with apical growth, 

 which may remain undivided or become divided into cell-rows 

 by septa, or transverse membranes. 



They are best known and classified by the forms of their 

 reproductive structures, which are generally sub-aerial, as in 

 the common mushroom ; but the mass of the hyphae grows and 

 spreads through living or rotten wood, in humus, or other 

 media, forming a collective growth termed a mycelium. The 

 mycelia of fungi may consist merely of branching hyphae, but 

 large masses of mycelium are sometimes formed in hollows of 

 rotten wood, as by Polyporus sulphur CMS, Fr. 



The reproductive organs of fungi are often formed on special 

 branches of the hyphae termed sporocarps, certain cells of 

 which produce myriads of isolated cells or spores, which on 

 escaping into the air or soil are capable, under suitable con- 

 ditions, of giving rise to new individual fungi. Spores may be 

 produced either sexually, or asexually by division, the latter 

 mode being by far the commoner, the spores thus formed by 

 the abscission of cells at the terminal points of hyphae being 

 termed conidia. For an account of the formation of sexual 

 spores (carpospores] special books* may be consulted. Among 

 them are certain thick-walled spores termed oosporcs, or 

 resting spores, which are rich in nutriment and, unlike 

 conidia, do not germinate as soon as they are mature, but 

 may remain dormant for prolonged periods, as in Phytophthora 

 Fagi, E. Hrtz. Sporidia are secondary spores produced by 

 promycelium by the germination of resting spores. 



As a rule, conidia remain only for a few days in a condition 

 fit to germinate and produce new individuals, but they appear 

 in immense numbers in the air or soil, are of microscopic size, 

 and are sometimes carried for miles by wind or water, or even 

 by men and animals. Infection may also be conveyed by 

 seeds in the case of certain rusts, which Dr. Cook} says attack 

 seeds, such as those of celery, wheat, or hollyhock by 

 various species of Puccinia. The resting spores are usually 

 larger than the conidia, better protected and richly provided 



* Dr. K. Goebel's " Outlines of Classification of Special Morphology <>r Plants.* 1 

 Translation by H. E. F. Garnsey, Oxford Clarendon Press, 1817. Do I'.ary, 

 " Morphology and Physiology of Fungi," etc., same translator and publisher. 



f Gardeners' Citron., 13 May, 1905. 



