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as being the original typical condition, this filament being drawn out, or 

 short and bulky, according to whether growth has taken place rapidly or 

 slowly. The basal tubercle of the mature prothallus when present would, 

 according to this view, be the result largely of secondary cell-divisions 



Fig. 61.^L. rmnulosum. Very j'ouiig prothallus, in general view, with spore still 



attached, x 75. 

 Fig. 62. — L. ramulosum. Young prothallus, in general view, showing basal tubercle 



with no fungus. X 45. 

 Figs. 63, 64. — L. ramulosum. Young prothalli, in general view, showing basal tubercle 



with fungus. X 30. 

 Fig. 65. — L. ramulosum. Young prothallus, in general view, showing first-formed 



lobes and the initiation of a second fungal region, x 45. 



which had taken place in the first-formed basal cells owing to the stimulus 

 excited by the storing of food material. Prothalli cultivated under arti- 

 ficial conditions seem generally to develop slowly, and this may explain 

 why it is that none of Treub's prothalli showed a first-formed filamentous 



