550 TRANS. ST. LOUIS ACAD. SCIENCE. 



one-third of their length, and presenting all the characters of spiral ves- 

 sels. These fascicles usually contain from five to twenty tubes ; each 

 tube inclosing one, two, or occasionally even three spiral fibres, which 

 adhere closely to the membrane." 



It may be well in this connection to quote from Dr. Gray t^"" 



" The ' mucilage ' so copiously developed on the surface of the seed 

 when immersed in water, and which gave name to the genus, consists of 

 innumerable and most delicate diaphanous tubes, which lengthen won- 

 derfully when wetted. The spiral thread which they contain (on which 

 account they were confounded with ' spiral vessels,' and which uncoils as 

 the tube softens or dissolves into jelly) is wanting in one species, namely, 

 C. gracilis. In this and in the several following species, the mucilage 

 cells are beneath a more or less evident pellicle or epidermis, composed 

 of fragile tabular cells, which are thrown off" when the former develop 

 and protrude under moisture. But this pellicle is not obvious in the 

 typical species." 



The fruits of some of the Labiatce are also provided with mu- 

 cilaginous epidermal cells which produce spirals on being 

 moistened with water. These have been studied by Schleiden.^i 

 Nageli,32 Schenk,33 Hofmeister,^* Frank, 35 Harz,35« Bal- 

 four,"^ &c. 



In some of the species of the genus Salvia, as in the subgenus 

 Echinosphacca.,'^^'^ the nutlets are abundantly mucilaginous. 

 Schenk, however, finds that in Lavandula^ L. Stcvchas is pro- 

 vided with epidermal cells which swell in the presence of water, 

 while L. Spica does not. The same is true of Plcctaiithra 

 glaitcocalyx and P. parvijiorus. Other genera of Labiatce pro- 

 vided with these structures are Ocinitim., Dracocephaluin., Ca- 

 lamiiitha., Melissa., Plcctranthus., and Lallemantia. Lessing^r 

 found that the hairs on the achenes of some Compositce are 

 provided with mucilaginous spirals. They have also been the 

 subject of a paper by Macloskie."?" 



30a. Proceedings of the American Academy, viii., 1S70, p. 25S. 



31. Beitrage zur Botanik, Leipzig, 1S49, p. 137. 



32. Ueber^len innern Bau vegctabilisclier Zellenmembranen. Sitzungsberichte der K. 

 bayr. Akad. d. Wissenschaften zu Aliinchen, \i.(>^, vol. ii., Heft ii., pp. 1 14-170, 3 plates. 

 See p. 114-123, PI. I. 



33. Zur Kenntniss des Baues der Friichte der Compositen und Labiaten. Bot. Zeit. , 

 1S77, p. 409-415. E. Loew. Just Bot. Jahresb. 1877, p. 320,321. 



34. L. c, p. 26-27. 



35. L. c, p. 169, 170, 171. 

 3Sa. L. c, p. S67, S6S. 



36. Class-Book of Botany. Edinburgh, 1S71, p. 19. 



36a. Gray: Synoptical Flora of North America, vol. ii., p. 366. 



37. See Kippist, 1. c, p. 65. 



37a. "Achenial Hairs and Fibres of Compositae," Am. Naturalist, vol. xvii. pp. 31-36. 



