36 FIELD MUSEUM or NATURAL HISTORY BOTANY, VOL. IV. 



A species with very unique aspect of foliage as well as of fruit. Speci- 

 mens of the type collection had been determined by E. L. Greene as 

 X. calijornicum Greene (cf. p. 35, footnote 2). But a study of Greene's 

 type of X. californicum shows no approach in fruit characters to the 

 type of X. calvum. We have seen several sheets of X. pennsylvanicum 

 having fruits typical of that species but with foliage offering a perplexing 

 resemblance to that of X. calvum (e.g., C. F. Baker 1512, along borders 

 of marshes, Palo Alto, California, Hb. Gray; Harley P. Chandler 5399, 

 Escondido, California, Hb. Calif. 64835). Future investigation upon the 

 status of such forms, which are possibly hybrids, would seem highly 

 desirable. 



The specific designation calvum is given in allusion to the bald or 

 smoothish appearance of the body and prickles of the mature fruit. 



14. XANTHIUM PALUSTRE Greene, Pittonia 4: 63. 1899. 



Caulis glaber aut paulo scabridus, interdum rubescens, saepe lineis 

 purpureis longitudinalibus maculatus, verisimiliter 0.5-1 m. altus. 

 Folia ovato-cordata aut deltoidea, dentata, plus minusve lobata, utrin- 

 que setulis minutis adpressis scabra, petiolis adjectis 0.8-3 dm. longa, 

 petiolis laminas subaequantibus aut excedentibus. Fructuum (PI. VII, 

 f. 14; PI. IX, ff. 13-15) corpus viridi-fuscum, demum crasso-oblongum 

 et nitens, glandulosum sed parce pubescens, circ. 1.8 cm. longum et 

 89 mm. crassum, aculeis brevibus armatum; rostris brevibus, crassis, 

 pubescentibus, supra incurvatis, ad apicem saepe subhamosis, 3-5 mm. 

 longis; aculeis numerosis sed vix confertis, versus basim crassum glandu- 

 losis et saepe sparsim pubescentibus, supra tenuibus et glabris, ad 

 apicem hamosis, 2-2.5 (ranter 3-3.5 aut etiam -4) mm. longis. 



DISTRIBUTION : California. 



SPECIMENS EXAMINED: CALIFORNIA: Suisun Marsh, in 1893, Edw.L. 

 Greene (Hb. Greene 19833 and 19834; type sheets); Lathrop, Harriet A. 

 Walker 926 (Hb. Calif. 201224); Suisun, eadem 973 (Hb. Calif. 128022). 



In Greene's Herbarium are two specimens to represent this rare and 

 little known species, both of them collected by Greene himself at Suisun 

 Marsh, and which may properly be taken as the types of the species. 

 These have fruits just as described by Greene, except that they are more 

 nearly oblong than he implied and had best not be described as "slightly 

 obovate-oblong." Furthermore, they tend toward a greenish-brown in 

 color, with some of the prickles becoming reddish. 



The first specimen by Miss Walker (listed above) is, in our opinion, 

 clearly X. palustre, but it shows an approach toward X. pennsylvanicum 

 Wallr. in having prickles 3-3.5 (a few even 4) mm. long. Miss Walker's 

 second specimen (no. 973), however, comes from the type locality and 

 matches the two type specimens identically, both as to foliage and as to 

 fruits. 



