NOTES UPON AN APOSPOROUS LAST RE A. 470 



Notes upon an Aposporous Lastrea (JVephrodinm). 



By C. T. Druery, F.L.S. 



[Eead 3rd November, 1892.] 

 (Plate XXXIV.) 



The term apospory has been applied to two abnormal modes of 

 reproduction discovered within the last few years upon certain 

 varietal forms of Athyrium Filix-foemina and Polystichum annu- 

 lare, and subsequently upon some exotic species. In the Athy- 

 rium {A. Filix-foemina, var. clarissima) the usual sites of the sori 

 are occupied by clusters of cellular excrescences furnished with an 

 indusium, and formed by abnormal development of the sporangia. 

 These excrescences, by expansion of their tips, grow out into 

 normal prothalli which produce plants of the approximate parental 

 type when pegged down upon the surface of suitable soil. The 

 spore is thus eliminated from the life-cycle. I exhibit a panful 

 of pinnae showing the early stages of development of the prothalli. 

 In the case of the Polystichums, of which several examples exist, all 

 of similar type (i.e. P. angulare, var. pulcherrimum), though found 

 as solitary sports in widely separated localities, a similar type of 

 soral apospory is found upon some of them; but they are further 

 characterized by prothalli being also formed independently alto- 

 gether of the sorus by simple extension of growth of the apices of 

 the ultimate divisions of the fronds, or more rarely upon extruded 

 venules near their extremities. These prothalli, however, can 

 scarcely be considered as normal, being very eccentric in shape ; 

 and though archegonia and antheridia are produced, and plants 

 have been raised by their interaction, these differ widely from 

 e parental type, are weakly in constitution, and irregular in 



* 



growth or form. The plants which I have raised from the soral 

 outgrowths of P. angulare, var. pulcherrimum, Moly, are also 

 defective and lacking in vigour. This, however, is not the case 

 with the Athyrium, the aposporous offspring of which are robust 

 and fairly typical. It was my good fortune to discover soral 

 apospory in Athyrium Filix-foemina, var. clarissima, and Mr. G. 

 B. Wollaston followed with the discovery of apical apospory in 

 Polystichum angulare, var. pulcherrimum, Padley; and in the 

 latter it will be seen that the life-cycle is still more shortened by 

 the elision of not merely the spore, but of the sporangium and 

 entire soral apparatus. 



So far the phenomenon has only been remarked on adult plants, 



LINN. JOVRN. BOTANY, VOL. XXIX. 2 N 



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