OCTOBKB 19, 1900.] 



SCIENCE. 



581 



discharge of the spores. Those fungi that 

 produce their spores directly upon the sur- 

 face through the stomata have their area of 

 sporification defined by the distribution of 

 the stomata and the veins and veinlets be- 

 come boundary lines in many instances. 

 When the fungus has the habit, as in the 

 rusts, of massing the sporiferous hyphse be- 

 neath the epidermis a new set of conditions 

 is introduced. It is found in such, by mi- 

 croscopic examination, that the portion of 

 the host just beneath the rupture is almost 

 entirely replaced by the dense plexus of 

 fungus hyphse, and the host tissue is de- 

 stroyed and the immediate threads are not 

 favorably situated for further growth. At 

 a short distance from the sorus in all direc- 

 tions the vitality is probably greater and 

 new points of spore -production are estab- 

 lished, resulting in a secondary circle of 

 sori surrounding the original spore-spot. 

 The development of this circle may be fol- 

 lowed by a second ring of sori, each sorus 

 more or less crescent-shaped until the host 

 shows ' fairy rings ' as real as those in the 

 lawn or meadow and for a similar reason. 

 Plants showing this concentric growth and 

 fruitageof its fungous parasite arenumerous. 

 Among those best illustrating the phenome- 

 non are Gystopus candidus (P.) upon Bursa, 

 Nasturtium, and several other Cruciferse ; 

 Pucainia asparagi DC. upon Asparagus offi- 

 cinale L.; Puccinia Arenaria (Schum) on 

 Dianthus barbatus L. ; and Puccinia Hieracii f 

 upon Chrysanthemum Sinense Sab. All of 

 these were shown by means of microphoto- 

 graphs. 



An Anthraenose and a Stem Rot of Antirrhinum 



majus : By F. C . Stewart. 



Antirrhinum majus is subject to two de- 

 structive diseases : (1) An anthraenose 

 caused by a new species of Colletotrichum for 

 which the author proposes the name Colleto- 

 trichum antirrhini; (2) A stem rot caused by 

 an undetermined species of Phoma. 



The Colletotrichum is destructive to plants 

 of all ages, at all seasons, both in the green- 

 house and in the field. It produces numer- 

 ous elliptical depressed spots on the stems 

 and circular dead brown spots on the leaves. 

 It fruits sparingly, except in a very moist 

 atmosphere. It has been successfully com- 

 bated by spraying the plants once a week 

 with Bordeaux mixture. The Phoma at- 

 tacks the stems, causing sections an inch or 

 more in length to turn brown or black. The 

 attack may be made at any point on the 

 stems above ground but is most likely to 

 occur a few inches below the tips of succu- 

 lent shoots. The portion of the shoot be- 

 yond the point of infection quickly wilts 

 and dies. Inoculation experiments with 

 pure cultures of the Phoma have shown that 

 it is an active parasite on succulent shoots 

 but attacks woody stems with difliculty. 



Notes upon Peltandra rust, Cceomurus Caladii 

 (Schw. ) Kunze Abstract : By F. H. Blod- 



GETT. 



This rust was very abundant in the aecid- 

 ial stage about the 15th of May, in a bed of 

 hardy aquatics within the New York Bo- 

 tanical Garden. Some leaves were infested 

 upon nearly every plant in the bed, and 

 upon some, all the leaves were infested. 

 Usually the upper portion of the petiole 

 was most severely attacked. In the worst 

 cases the midrib and its branches, and the 

 petiole nearly to the water would be covered 

 with the aecidia. In such cases the plants 

 suffered severely from a bacterial rot affect- 

 ing first the stems at those points most 

 rusted, thence spreading, until the stem 

 rotted away. Uredosori were not observed 

 until June 7th; they became gradually more 

 abundant, but at no time were they so viru- 

 lent or so conspicuous as in the earlier stage. 

 The uredosori were confined in manj' cases- 

 to the blade of the leaf, although occasion- 

 alljf found on the midrib and petiole. The 

 uredospores bear a decided resemblance in 



