— 356 — 



green, particolored or entirely etiolated according to their origin 

 respectively opposite a green part of the leaf, astride the intersection 

 of green and white, or entirely opposite the latter. The constancy 

 of A. picfa, A. americana manjinafa, etc., however, seems to show that 

 except in incipient variegations, in which this may perhaps occur, 

 the meristem initials of the etiolated parts are so inherently fixed 

 in distribution as to perpetuate with general constancy the ancestral 

 type of variegation. 



St. Louis, Missouri, U. S. A., August 31, 1907. 



Explanation of Plates. 



VI. Agave americana. — Above: Three thick sections, at different 

 distances from the base, of var. sfriata. — Below: Sections, near 

 the base, of var. marginnta and var. medio-picta, — the middle figure 

 representing the more striate form of the latter. (All X 2). 



VII. Agave americana marginata, at right, and A. i)icfa, at left. 

 Very young plants, but well contrasted. (X V^)- 



T7/i. Agave angustifoUa marginata, Cultivated in the Botanical 

 Garden, Dominica. (X Vn). 



IX. Agave Hookeri striata. Cultivated at the Royal Gardens 



Kew. (X 1/5). 



X Agave albicans medio-picta. Cultivated at the Royal Gardens, 

 Dahlem, near Berlin. (X Vi)- 



AT. Agave Morrisü marginata. Cultivated at the Royal Gardens, 

 Kew (X V15). 



XU. Agave fourcrogdes medio-picta. Cultivated at the Missouri 

 Botanical Garden. A two-year-old bulbil plant, not yet showing the 

 mature characters of the species. (X 'A,). 



Explanation offigures in the Text. 



The spine and marginal teeth are of natural size. — The cross 

 section of a leaf-fragment of Agave americana medio-picta shows 

 the abrupt cessation of the chlorenchyma at the edge of the variegation- 

 band (X 100). 



