INTRODUCTION TO CRYPTOGAMIC BOTANY. 307 



abundant everywhere, make a slight approach to the brown 

 or cinereous tint, which in its extreme condition indicates the 

 group which follows ; a group, even to the external eye, most 

 evidently distinct. As in the former tribe the spores and 

 mycelium were the grand object of development, here the 

 fertile threads, with their fruit-bearing apparatus, have decidedly 

 the pre-eminence. In the genus Botrytis, with its various 

 sub-genera, the fertile threads are rarely simple, and the 

 ramifications frequently beautifully regular and highly curious. 

 The spores are often large in proportion, but simple. There 

 is no tendency in the higher species to form any compact head, 

 thotigh the fructifying ramuli are decidedly collected into a 

 distinct truss. In Penicilliwm, the spores are no longer soli- 

 tary, but necklaces of greater or less length, consisting fre- 

 quently of very numerous spores, cover the tips of the fertile 

 ramulL In Aspergillus (Fig. 68, a, h), as in Penicillium 

 (Fig. 68, c), the reproductive bodies are arranged in threads, 

 but all the fertile threads are crowded into one more or less 

 compact* globose body, so as to form little powder puffs. 

 In other instances, the branches are symmetrically arranged 

 in whorls, sometimes so short as to be mere points on which 

 the spores are seated, offering a most elegant appearance, com- 

 parable with that of Batrachospermum. In one of these the 

 spores are septate, and in Dactylium the articulations are 

 sometimes numerous. 



327. Their habits are as various as their external characters. 

 The most inaccessible cavities are not free from their presence, 

 and they occur on living structures, as well as those which are 

 in a state of decay. This true parasitism of some of the species 

 renders them, like other real parasites, capable of producing 

 material injury where they occur in any abundance. Unwilling 

 as the scientific world has been to allow the agency of Fungi 

 in the potato murrain, as regards that, as well as the grape 

 mildew, there are few dissentient voices now, amongst those 

 who understand the subject. The mycelium flourishes in the 

 large intercellular spaces of the leaves, but penetrates also into 

 • The heads oi Aspergillus, studded with sporophores tipped with sterig- 

 mata (Fig. 68, 6), are analogues, bet not homologues of an hymenium. 

 20 * 



