MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



75 



with walls thickened to such an extent as to almost obliterate the 

 lumina in same instances. The etiolated stem presents a marked 

 contrast in this matter. Only four or five layers of the pericycle 



19 ^'^^SvS 



cPX)^ 



D 





II 



M^ 



mOfftr 



Fig. 29. I, partial transverse section of normal stem of Asparagus officinalis. II, 

 partial transverse section of etiolated stem. A, epidermis. B, cortex. C, pericycle. 

 Z), region in which large bundles are seen. 



are noticeably thickened and the walls have but a fraction of the 

 diameter of the normal. The steles 

 in the central portion of the etio- 

 lated stems showed least departure 

 from the normal. Those lying ex- 

 ternally, however, remained in a 

 primitive stage of development. 

 The spiral vessels were best differ- 

 entiated, while the great annular 

 vessels had very thin walls. The 

 sieve tissues also showed a lack of 

 differentiation, and their contents 

 were not so dense as in the normal. 



Asplenium platyneuron (L.) 

 Oakes. 



Rhizomes collected at New Ca- 

 naan, Conn., November 27, 1900, 

 were placed in the dark room at once, and showed indications of 

 activity within a few weeks. Fronds curved in the form of an open 

 spiral of one and a half revolutions with a midrib 20 cm. long were 



Fig. 30. Asplenium platyneuro?t. 

 Normal. After Britton and Brown. 



