A manual of British lichens : containing descriptions of all the species and varieties / by William Mudd.

  • Mudd, William.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: A manual of British lichens : containing descriptions of all the species and varieties / by William Mudd. Source: Wellcome Collection.

    23/356 (page 11)
    strengthened in this opinion from the fact, that the majority of spores, when mature, contain very little of the first ingredient, and in a large number none of it. To this there is, however, some exception, as we sometimes see all the spores of an apothecium, when mature, filled with these minute granules: we account for this from the fact, that the asci of such species originally contained a large portion of these granules, and only a small one of the others, consequently, the superabundance not being required in the formation of the spore-walls, it remains mixed up with the other ingredients in the interior of the spores ; hence their granular aspect. After the formation of the external spore-wall has taken place, the spores become distinct, and free of all internal ad- herence, and possess a definite outline. If the now newly-formed spore is to consist of only one cell or loculus {unilocular—see pi. \,ji(js. 1, 2, 11, etc.^, nothing further than a little consolidation of the spore-wall, and a slight expansion of the ascus is required for its completion ; after which it becomes fully ripe and ready for expulsion, or, in other words, a perfected body, fit to germinate and produce the species to which it appertains. But if the internal organizable matter is to be divided by some partition, Avhich is very frequently the case, the formation of these partitions commences immediately after the completion of the external spore-wall. BiJocular spores are formed by a partitional membrane, being drawn directly across the transverse diameter of the spore, which, on its completion, divides the internal organizable fluid into two loculi of an equal size {seepi. 13). If a quadrilocular spore is contem- plated, it is traversed by three transverse partitions—one in the centre, the others towards each end, at about an equal distance from the central one {seepi. ^,Ji(J. 6) ; and whatever other number of loculi may be required, their formation is generally effected in the same manner, except in the case of the polari-hilocular and muriform-multilocular spores. The polari-hilocular spores have an elliptical outline after the formation of the external spore-wall has been accomplished, and are filled with organizable fluid, which becomes divided by two partitional membranes, both of which are at first placed close together, and after having stretched across the entire breadth of the spore, each membrane then recedes in an opposite direction, and draws the internal fluid to the ends or poles of the spores, and thus, on their completion, they resem- ble the arctic and antarctic circles of a map of the globe {see pi. ^, fi(/. 41). It sometimes, however, happens that the whole of the internal matter of a spore is enveloped in only one internal membrane, the sides of which eventually contract, leaving a channel of communication be- tween the poles {see pi. ^,fi(j. 43rt); and at other times the contracting force of the internal membranes appears to be so strong as to cause a bulging of the extremeties beyond the elliptic outline of the spore {see ])l. ^ifiil. 42j. The formation of a spore of the muriform-multilocular type is effected by the Avhole of the internal fluid of a sj^ore (after the completion of the external spore-wall) being enveloped in an internal membrane, which eventually cleaves into 3, 5, 7, or more parts, the par- titions crossing the spore transversely, after which each becomes again divided by 1,2, 4, or more longitudinal partitions, and thus, on their completion, the internal organization resembles the stones in a wall; hence the origin of the term muriform-muliilvcular. I ought to say, however, tluit the longitudinal partitions are very often irregular, and do not always run in a straight line ; and that the corners also of the c 2