HTRTOLOGY OF LKnH"EA MAftlTIMA. 



497 



Epi<hrmis: Cells large, with thin, not undulate walls. Stomata 

 few on the ventral surface, much more numerous on the dorsal, lying 

 mostly parallel to the leafs axis, each bordered by four or five undif- 

 ferentiated epidermis cells. Hairs (fig. 88) on both surfaces, but 

 much more numerous and with more warty cuticle on the dorsal face, 

 long, rather stout, sharp-pointed, with very thick cuticle, contracted 

 shortly above the base, seemingly bicellular, the basal portion sepa- 

 rated from the rest of the lumen by a membrane which is convex 

 toward the apex of the hair, the lower portion about one-half as long 

 as the upper, base of hair bordered by several 

 radially arranged footcells. Man}' of the epider- 

 mis cells on both faces are greatly enlarged, 

 and probably serve for storage of water. 1 



Palisade in one layer on each face of the leaf. 

 Pneumatic tissue central. 



Hairs similar to those just described form the dense 

 covering of the leaves of Hvdsonia tomentosa, but iu that 

 species they are more slender and have a smooth cuticle. 

 They also occur in Helianthum canadense (which see). 

 Solereder'' describes hairs of this character in Lechea 

 major and Hndmnia ericoides, and figures one from the 

 leaf of Cistus creticus, in which, however, the basal por- 

 tion of the lumen cut off by the dividing membrane is 

 proportionately much shorter than in Lechea maritima. 

 He found that Eau de Javelle stains the dividing mem- 

 brane yellow, while the walls of the original cell remain 

 white. He states that this type of hair is peculiar to 

 Cistaceae and Combretaceae. 



A very interesting description of these falsely bicel- 

 lular hairs in Combretaceae is given by Heiden, 3 who 

 found them so characteristic in that family that he terms 

 them "Combretaceae hairs.' - Thiloa is apparently the 

 only genusof Combretaceae in which they are even rare. 

 Heiden's description is as follows: 



"But what is characteristic of these hairs is the cir- 

 cumstance that the mostly somewhat bulbous-swollen 

 base is separated from the principal part of the hair, 

 which is filiform, by a layer of cellulose which projects 

 more or less convexly or conically toward the latter. 



So in many cases it seems as if the Combretaceae hairs in question are not one- 

 celled, but rather two-celled. 



"That these apparently two-celled hairs are not to b«i regarded as two-ceiled is 

 very clearly shown by their development. 



"The first stage of development here considered (see plate fig. la) consists of an 

 already pretty thick-walled, long-pointed, one-celled hair, whose lumen widens out 

 in the lower part, while in the upper part it is almost filiform. The entire lumen 



KlO. 88. — Lechea Maritima. 

 Falsely bicellular hair 

 from loaf. MagnifiodJIfiO 

 times. 



1 Solereder (Syst. Anat., p. 91) mentions similarly specialized epidermis cells in 

 L. minor L. (Lechea novae- cesareae Aust.). 

 2 Syst. Anat., p. 91./. 21 A. 

 3 Bot. Centralhl., vol. 55, pp. 358, 359, and vol. 56, p. 64, /. /, 1893. 



