1902] A MORPHOLOGICAL STUDY OF ASCLEPIADACEAE 391 



The glands do not seem to have been observed by Schacht 

 (10), although they are easily seen with a hand lens. Chauveaud 

 (3) saw them within the calyx of Cynanchum, and gives their 

 structvire and formation without attempting to explain their 

 function or stating their number. Schumann (11) in charactei- 

 izing the genus Asclepias says the glands within the calyx are 

 paired or single, but makes no mention of their occurrence else- 

 where on the plant. 



In all the species studied, between the calyx and corolla and 

 alternating with the members of the former, groups of glands 

 were found. In the mature flower there are from one to six in 

 each group, the number and size varying even in the same flower. 

 Usually they are side by side {^fig> 5), but sometimes they are 

 radially placed {fig. <5). They are also scattered singly on the 

 swollen top of the common peduncle. Near the base of a bract 

 of the involucre on its adaxial surface as many as a dozen may 

 be found {fig. 7). Dr. H. C. Cowles called my attention to 

 their presence in A. Sidlivantiiy in the axils of the leaves, and 

 and also near the base of the lamina on the adaxial surface of 

 the midrib. I have observed them at the latter point in her- 

 barium specimens oi Asclepias speciosa, A. exaltata, A, Sullivantii^ 

 A. Cornutiy A. jalisca?M, A, arenaria, and would not be surprised 

 if careful examination revealed them in many others. 



Taking the development of the glands inside the sepals as an 

 illustration, they appear about the time the carpels begin to 

 show, but on other parts of the plant they appear earlier. At 

 first there is only one representing each group, and it arises from 

 the sepal on its adaxial surface quite near the base and lateral 

 edge. Later others appear on each side of the first and thus 

 the group is formed. The middle (oldest) ones usually remain 

 the largest. In their formation {figs. 3, 4) the division of the 

 hypodermal cells forms a protuberance of isodiametric cells over 

 which the epidermis continues. The elongation of the interior 

 cells then increases the length of the protuberance, while the 

 epidermal cells elongate radially over the whole or a part of the 

 surface and function as gland cells, as is shown by their deep 

 stain, volume of protoplasm, and large nuclei {fig. 8). These 



