Holloway. — Protocorm of Lycopodium laterale. 73 



Art. IX. — Preliminary Note on the Protocorm of Lycopodium laterale 



R. Br. Prodr. 



By J. E. Holloway. M.Sc. 

 [Rend before, the Philosophical Institute of Canterbury, 2nd December, 1014.] 



It is well known that in the embryo plant of Lycopodium cernuum, and also 

 in those of L. inundatum and L. salakense, the development of the tuberous 

 organ termed the " protocorm " is an important phase in the ontogeny, 

 bridging over the period between the early stage in which the embryo 

 plant is wholly dependent upon its parent prothallus, and its subsequent 

 development, in which it has obtained independence through the establish- 

 ment of a root-system. Moreover, in the related genus, Phylloglossum, a 

 protocorm is present, and this plant has been spoken of as " a permanently 

 embryonic form of Lycopod," for the protocorm is there not a temporary 

 organ, but the plant-body proper. 



The Lycopod protocorm is the subject of widely differing interpretations. 

 The first of these, and one which invests this organ with considerable interest 

 and importance, is that it is a highly primitive organ, and represents an 

 ancestral phase in the evolution of the free-living Lycopodium sporophyte, 

 and perhaps also in the evolution of vascular plants generally (Treub). 

 A second interpretation is that the protocorm is not to be regarded so 

 much a primitive organ as an opportunist growth, and that, even if it does 

 play an important part in the establishment of certain Lycopod embryos, 

 it is not to be regarded as representing a phylogenetic feature in the Lyco- 

 pod iaceae, and still less in vascular plants as a whole (Bower). A third 

 interpretation has more recently been put forward, which, taking into 

 account the great development of the stem in Palaeozoic Lycopods, and 

 being unwilling to regard the protocorm either as a highly primitive organ 

 or as a mere parenchymatous swelling, would look upon it as a modified 

 form of stem due to reduction (Brown, "New Phytologist," vol. 12, p. 222, 

 June, 1913). 



In view, therefore, of the puzzling nature of this organ, it is interesting 

 -to note that it has been found in yet another species of Lycopodium — viz., 

 L. laterale — and that it there assumes a much greater size, and plays a much 

 more important part in the establishment of the young plant than in the 

 other species of Lycopodium in which it has been recorded. 



In a paper entitled " A Comparative Study of the Anatomy of Six New 

 Zealand Species of Lycopodium" published in the Transactions of the New 

 Zealand Institute, vol. 42, 1910, the writer gave a short account of the 

 protocorm of L. laterale, with five small figures (figs. 5-9, pi. xxxi). No 

 definite conclusion was there reached as to the interpretation of the proto- 

 corm. The present paper is a summary of the writer's further observations 

 upon this organ. 



The prothallus of L. laterale is of the cernuum type, as is the case 

 also for the prothalli of each of the other species in which a protocorm 

 has been found, excluding the possibly doubtful case of L. phlegmaria. 

 At the stage at which the young plant of L. laterale consists of a basal 

 protocorm surrounded by two or three protophylls it is similar in appear- 

 ance to the voung plant of L. cernuum. The succeeding stages in its 

 development are, however, noteworthy. The protocorm grows sideways, 

 •owing to the lateral development of two new protophylls, whose swollen 



