574 Goodlatte: The anatomy of Parosela spinosa 



spine and a shoot. Thus, with very few exceptions, in the mate- 

 rial examined, there was a regular alternation ; first, an axillary 

 shoot, becoming the axis, the main axis being arrested and devel- 

 oped into a spine, then a fork with both axis and shoot developing 

 into equal branches, then again, on each of these a spine and a 

 shoot, and so on. At the growing tip it can be seen that the 

 transformation of axis into spine takes place at a very early stage, 

 the tip becoming horny and the stereome tissue strongly developed 

 before the shoot is well out of the enfolding leaf and considerably 

 before the formation of the axillary shoot which is to take its place 

 as axis. 



The most striking internal characters are, in general, the great 

 development in the stem of chlorophyl-bearing tissue to assume 

 the functions of the fugacious leaves, the occurrence in great num- 

 bers of crystals of calcium oxalate, and especially the very general 

 distribution and prominence of glands and secretory apparatus. 



The leaves, as has been said, remain on the plant only a very 

 short time, and are comparatively few, even in the season. The 

 minute paired stipules each have a large, persistent gland at the 

 base, of the same anatomical character as the glands which are 

 scattered irregularly over the stem and leaf. The hairs cover both 

 surfaces of the leaf, clustering most densely in an irregular arrange- 

 ment around the stoniata. Weyland finds it characteristic of the 

 tribe of the Galegeae, almost without exception, that the stomata 

 are surrounded by cells arranged without any special order, neigh- 

 boring the guard cells. P, spinosa possesses this character in 

 common with the rest of the tribe. The stomata occur on both 

 surfaces of the leaf, but are more numerous on the under side. 

 They are simple in type, the guard cells not being even deeply 

 sunk, though their outer walls are heavily cutinized, in common 

 with the other epidermal cells. 



In addition to this layer of cutin, the epidermis of the leaf is 

 noteworthy because of the occurrence of rhomboidal crystals of 

 calcium oxalate in a few of its cells. In regard to the shape of the 

 crystals found by him in the epidermis of the single species Dalea 

 versicolor Zucc, Weyland describes them as being short and rod- 

 shaped, the cells containing them lying either singly or in groups, 

 and being smaller than the surrounding cells. In P. spinosa, 



