CHAPTER V.— COMPARATIVE REVIEW.- -ASCOMFCETES. 25$ 



important point here, the tendency to the reproduction of like forms, is not the less 

 manifest. 



Similar relationships appear to exist in Pleospora herbarum (or Gibelli's P. 

 Alternariae), but I cannot speak decidedly respecting them. By corresponding 

 relationships I should now be inclined to explain the facts, observed by myself 

 in connection with the reproduction of like forms in the gonidial form of Cor- 

 dyceps known as Isaria farinosa 1 , which led to a controversy respecting its con- 

 nection with the cycle of development of Cordyceps militaris, for which Tulasne 

 contended. 



Moreover it must easily happen, that in species which show the tendency in 

 question, this tendency and the external conditions work together in the same 

 direction, and the possible consequences of this co-operation can be readily con- 

 ceived. The long-continued effect of the combined conditions might ultimately result 

 in the permanent separation of the originally connected forms, each preserving its 

 existence as a species. This means that each loses the other out of its cycle of 

 development, whether the other continues a separate existence or for any reason dis- 

 appears. It is quite conceivable that species of Ascomycetes producing gonidia only 

 like those described above might originate in this way. 



On the other hand, we have to consider that the two sets of causes determining 

 the production of forms in these Fungi, the external and the internal, also work in 

 opposite directions, and that the external causes may eventually overcome the internal 

 tendency and lead to the reproduction of the other form from the one first produced. 

 We may also imagine a priori that there are cases in which special conditions must 

 combine to produce this result, cases in which the few observations that we possess 

 do not acquaint us with the real conditions, though they are perhaps very simple. 

 Ten experiments may be made with a similar result under different conditions, and 

 the eleventh may all at once give a totally different result. Experiences of this kind 

 are quite common in this portion of the field of research. These facts admonish us 

 to be cautious, and require that the suggestions in the text should once more be 

 expressly declared to be only very guarded conjectures. 



Section LXXIV. No less caution is advisable in determining some of the 

 organs which have been described above as doubtful, and we must say a word 

 more about them in this place. The attempt has more than once been made to remove 

 the doubt which exists as to their real nature by declaring them to be rudimentary 

 (rudimentar). It will be well therefore to remember that organs or members are 

 said to be rudimentary which do not reach the height of development attained by their 

 homologues but are stunted in their growth, that is, remain stationary at a stage in 

 their development in which they are in every respect immature ; such are the 

 rudimentary stamens of Salvia and of some diclinous flowers. It is true that the term 

 rudimentary has been used in another sense, when an organ is highly developed, 

 but is not properly adapted to the function usually discharged by its homologues, 

 being applied to some other purpose through a necessity resulting from its high 

 organisation, as, for instance, the median staminode of Cypripedium. In some cases 

 this mode of expression may be obvious and therefore admissible, especially as there 



1 Bot. Ztg. 1867, 1869. 



