352 



LYCOPODIALES 



first year's growth. From the description of Thomas it thus appears that 

 the embryology is just what would be expected of a plant which had 

 already been recognised as repeating in its annual cycle a development 

 similar to that of L. cernuum. 



The yearly growth of Phylloglossum resembles in many features that 

 of the embryo : it originates at the apex of the storage-tuber formed 

 during the preceding year, and its punctum vegetationis retains its identity 

 as the centre of the new growth. Sometimes only a single leaf is formed, 



FIG. 1 88. 



A and B embryos of Lycopodium cernuum, showing protocorm. j^suspensor; 

 / = foot; cot = cotyledon ; _/', _/' 2 , etc. = successive leaves; ? root; vtpunctinn 

 vcgetationis. X 35. (After Treub.) 



but usually several more in strong plants : they arise in succession laterally 

 around the apex, but are definite neither in number nor in position. In 

 those cases where the plant does not form a strobilus, the apex, which 

 lies centrally among the leaves, becomes depressed, while the tissue 

 surrounding it, continuing to grow actively but unequally, a process is 

 formed which develops into the new tuber (Fig. 189 A, B). Where a 

 strobilus is formed it arises directly from the apex (Fig. 189 c, D, E), and 

 a new provision has to be made for the formation of the new tuber. 

 This appears adventitiously at the base of the peduncle, as a depression 

 which is carried outwards on an elongating process due to active and 



