THE ANATOMY AND AFFFNITY OF DEPARIA MOOREI, HOOK. 849 



at first sight appear to do so, are found, by microscopical examination, to stop just 

 short of the margin, or to end in thin-walled, elongated, parenchymatous cells, 

 evidently replacements of the storage tracheides typical of bundle endings. Similar 

 parenchymatous bundle endings are, moreover, sometimes found where two fine 

 branches of the reticulum approach each other, and though not actually uniting, 

 their tracheides are linked by a bridge of long, thin, parenchymatous cells. It is also 

 to be observed that in Deparia prolifera, with rare exceptions, the sori are all 

 marginal, but in Deparia Moorei, while the majority of the sori are truly marginal, 

 a number are scattered on the upper surface of the leaf. These superficial sori are 

 always terminal on the veins which bear them, and unless a vein — whether it reach 

 the margin or not — is provided with a sturdy ending of storage tracheides, it never 

 terminates in a sorus. Professor Farmer has appended a note to a specimen of 

 Deparia Moorei in Kew Herbarium, stating that the superficial position of the sorus 

 is most common in garden-grown plants. 



The thin texture of the lamina of Deparia Moorei, the less pinnatifid nature of 

 its pinnae, — compared with those of Deparia prolifera, — its recticulate venation, and 

 the fact that many of the bundle endings fall just short of the margin, or if they 

 actually reach the margin, lack the typical sturdy endings, have all their bearing on 

 the positions which the sori hold in Deparia Moorei. In fact, it is suggested that 

 they are part-cause of, or effects associated with, the occasional production of the sori 

 on the upper surface instead of in the truly marginal positions. I also believe that 

 unless a bundle ending which reaches the margin is from an early period adequate, 

 or unless the margin is itself at a very early stage sufficiently sturdy to support a 

 marginal sorus, such a sorus is seldom if ever initiated. This may account for the 

 fact that although a careful study was made of the development of the marginal sori, 

 no stages were found suggesting that a sorus had been initiated on the margin and 

 had been bodily removed at a later stage from its marginal position by the out- 

 growing of a new margin. All the stages observed went to prove that any portion 

 of the leaf margin on which a sorus was initiated, remained, throughout development, 

 an inherent part of the sorus itself. Each individual, superficial sorus may then be 

 regarded not as having been shifted inwards from the margin, but as a structure 

 which has been initiated in a new and independent position. 



In other words, the view is entertained that the superficial position of the sorus, 

 where it occurs, is not the result of a " phyletic slide," in the sense used by Professor 

 Bower in the Blechnoid Ferns (Ann. of Bot., July 1914, p. 386). On the other 

 hand, it will be shown from developmental stages, that the exact marginal position 

 in which the sorus originates is liable to alteration in the course of development, so 

 that when mature, it faces obliquely upwards : a point of difference from many 

 other ferns whose sori are of marginal origin, and in which the mature sorus faces 

 obliquely downwards. 



